0000000000037046
AUTHOR
M. Vesterinen
showing 242 related works from this author
Combination of searches for anomalous top quark couplings with 5.4 fb−1 of pp¯ collisions
2012
We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in t (t) over bar events. We set upper limits on anomalous tWb coupling form factors using data collected with the DO detector at the Tevatron p (p) over bar collider corresponding to an integrated luminosity of 5.4 fb(-1).
Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States
2011
Made available in DSpace on 2022-04-29T01:13:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-10-05 National Science Foundation We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2fb-1 of pp̄ collisions at √s=1.96TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L. © 2011 American Physical Society. Universidad de Bu…
Evidence for the decay X(3872)→ψ(2S)γ
2014
Evidence for the decay mode X(3872) -> psi(2S)gamma in B+ -> X(3872)K+ decays is found with a significance of 4.4 standard deviations. The analysis is based on a data sample of proton proton collisions, corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb detector, at centre-of-mass energies of 7 and 8 TeV. The ratio of the branching fraction of the X(3872) -> psi(2S)gamma decay to that of the X(3872) -> J/psi gamma decay is measured to be B(X(3872) -> psi(2S)gamma)/B(X(3872) -> J/psi gamma) = 2.46 +/- 0.64 +/- 0.29, where the first uncertainty is statistical and the second is systematic. The measured value does not support a pure D (D) over bar* molecular interpre…
First observation of a baryonic Bc+ decay
2014
A baryonic decay of the $B_c^+$ meson, $B_c^+\to J/\psi p\overline{p}\pi^+$, is observed for the first time, with a significance of $7.3$ standard deviations, in $pp$ collision data collected with the LHCb detector and corresponding to an integrated luminosity of $3.0$ fb$^{-1}$ taken at center-of-mass energies of $7$ and $8$ $\mathrm{TeV}$. With the $B_c^+\to J/\psi \pi^+$ decay as normalization channel, the ratio of branching fractions is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+\to J/\psi p\overline{p}\pi^+)}{\mathcal{B}(B_c^+\to J/\psi \pi^+)} = 0.143^{\,+\,0.039}_{\,-\,0.034}\,(\mathrm{stat})\pm0.013\,(\mathrm{syst}). \end{equation*} The mass of the $B_c^+$ meson is dete…
Combined Tevatron upper limit ongg→H→W+W−and constraints on the Higgs boson mass in fourth-generation fermion models
2010
We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg -> H -> W+W- in p (p) over bar collisions at the Fermilab Tevatron Collider at root s = 1.96 TeV. With 4.8 fb(-1) of integrated luminosity analyzed at CDF and 5.4 fb(-1) at D0, the 95% confidence level upper limit on sigma(gg -> H) x B(H -> W+W-) is 1.75 pb at m(H) = 120 GeV, 0.38 pb at m(H) = 165 GeV, and 0.83 pb at m(H) = 200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.
Measurement of the Effective Weak Mixing Angle inpp¯→Z/γ*→e+e−Events
2015
We present a measurement of the fundamental parameter of the standard model, the weak mixing angle, in $p\bar{p}\rightarrow Z/\gamma^{*}\rightarrow e^{+}e^{-}$ events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of $\sin^2\theta_{\text{eff}}^{\text{$\ell$}}=0.23146 \pm 0.00047$ is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results.
Search for the Standard Model Higgs Boson in theZH→νν¯bb¯Channel in5.2 fb−1ofpp¯Collisions ats=1.96 TeV
2010
A search is performed for the standard model Higgs boson in 5.2 fb-1 of p-pbar collisions at sqrt(s)=1.96 TeV, collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered is a pair of b jets and large missing transverse energy, as expected from p-pbar->ZH->vvbb production. The search is also sensitive to the WH->lvbb channel when the charged lepton is not identified. For a Higgs boson mass of 115 GeV, a limit is set at the 95% C.L. on the cross section multiplied by branching fraction for p-pbar->(Z/W)H and H->bb that is a factor of 3.7 larger than the standard model value, consistent with the factor of 4.6 expected.
Search for the standard model Higgs boson in the ZH→νν¯bb¯ channel in 9.5 fb−1 of pp¯ collisions at s=1.96 TeV
2012
We present a search for the standard model Higgs boson in 9.5 fb-1 of ppbar collisions at sqrt(s) = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from ppbar->ZH->vvbb production. The search is also sensitive to the WH->lvbb channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section sigma(ppbar->[Z/W]H), assuming standard model branching fractions, that is a factor of 4.3 times larger than th…
Study ofB−→DK−π+π−andB−→Dπ−π+π−decays and determination of the CKM angleγ
2015
We report a study of the suppressed B- -> DK-pi(+)pi(-) and favored B- -> D pi(-)pi(+)pi(-) decays, where the neutral D meson is detected through its decays to the K--/+pi(+/-) and CP -even K+K- and pi(+)pi(-) final states. The measurement is carried out using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb(-1). We observe the first significant signals in the CP - even final states of the D meson for both the suppressed B- -> DK-pi(+)pi(-) and favored B- -> D pi(-)pi(+)pi(-) modes, as well as in the doubly Cabibbo suppressed D -> K+pi(-) final state of the B- -> D pi(-)pi(+)pi(-) decay. Evidence for the suppressed d…
Measurement of directCPviolation parameters inB±→J/ψK±andB±→J/ψπ±decays with10.4 fb−1of Tevatron data
2013
We present a measurement of the direct CP-violating charge asymmetry in B-+/- mesons decaying to J/psi K-+/- and J/psi pi(+/-) where J/psi decays to mu(+)mu(-), using the full run II data set of 10.4 fb(-1) of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. A difference in the yield of B- and B+ mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of A(J/psi K) = [0.59 +/- 0.37]%, which is the most precise measurement to date, and A(J/psi pi) = [-4.2 +/- 4.5]%. Both measurements are consistent with standard model predictions.
Observations of Bs0→ψ(2S)η and B(s)0→ψ(2S)π+π− decays
2013
First observations of the $B^0_s \rightarrow \psi(2S) \eta$, $B^0 \rightarrow \psi(2S) \pi^+ \pi^-$ and $B^0_s \rightarrow \psi(2S) \pi^+ \pi^-$ decays are made using a dataset corresponding to an integrated luminosity of 1.0~$fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The ratios of the branching fractions of each of the $\psi(2S)$ modes with respect to the corresponding $J/\psi$ decays are \[ \frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta) }{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} =0.83\pm0.14\,(stat)\pm0.12\,(syst)\pm0.02\,(\mathcalB}), \] \[ \frac{\mathcal{B}(B^0 \rightarrow \psi(2S) \pi^+ \pi^-)}{\mathcal{…
Measurement of theϕη*distribution of muon pairs with masses between 30 and 500 GeV in10.4 fb−1ofpp¯collisions
2015
We present a measurement of the distribution of the variable phi(eta)* for muon pairs with masses between 30 and 500 GeV, using the complete run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb(-1) at root s = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable phi(eta)* probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the phi(eta)* distributions for dilepton masses aw…
Search forWHassociated production inpp¯collisions ats=1.96 TeV
2012
This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L approximate to 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider. Events containing a W -> l nu candidate (with l corresponding to e or mu) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a b quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the WH production cross section and branching ratios and …
Search for Randall-Sundrum Gravitons in the Dielectron and Diphoton Final States with5.4 fb−1of Data frompp¯Collisions ats=1.96 TeV
2010
Using 5.4 fb-1 of integrated luminosity from ppbar collisions at sqrt(s)=1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider, we search for decays of the lightest Kaluza-Klein mode of the graviton in the Randall-Sundrum model to ee and gammagamma. We set 95% C.L. lower limits on the mass of the lightest graviton between 560 GeV and 1050 GeV for values of the coupling k/Mbar_pl between 0.01 and 0.1.
Measurement of theWZandZZproduction cross sections using leptonic final states in8.6 fb−1ofpp¯collisions
2012
We study the processes p (p) over bar -> WZ -> l(+) vl(+) l(-) and p (p) over bar -> ZZ -> l(+) l(-) v (v) over bar, where l = e or mu. Using 8: 6 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider, we measure the WZ production cross section to be 4.50(-0.66)(+0.63) pb which is consistent with, but slightly larger than, the prediction of the standard model. The ZZ cross section is measured to be 1: 64 +/- 0: 46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ -> l(+) l(-) l(+) l(-) channel yields a ZZ cross section of 1.44(-0.34)(+0.35) pb.
Measurement of three-jet differential cross sections dσ3jet/dM3jet in pp¯ collisions at s=1.96 TeV
2011
We present the first measurement of the inclusive three-jet differential cross section as a function of the invariant mass of the three jets with the largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96 TeV. The measurement is made in different rapidity regions and for different jet transverse momentum requirements and is based on a data set corresponding to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at the Fermilab Tevatron Collider. The results are used to test the three-jet matrix elements in perturbative QCD calculations at next-to-leading order in the strong coupling constant. The data allow discrimination between parametrizations …
Amplitude analysis ofB0→D¯0K+π−decays
2015
The Dalitz plot distribution of B-0 -> (D) over bar K-0(+)pi(-) decays is studied using a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. The data are described by an amplitude model that contains contributions from intermediate K* (892)(0), K*(1410)(0), K-2*(1430)(0) and D-2(*)(2460)(-) resonances. The model also contains components to describe broad structures, including the K-0(*)(1430)(0) and D-0(*)(2400)(-) resonances, in the K pi S-wave and the D pi S-and P-waves. The masses and widths of the D-0*(2400)(-) and D-2(*)(2460)(-) resonances are measured, as are the complex amplitudes and fit fractions for all components in…
Measurement ofCPviolation inBs0→ϕϕdecays
2014
A measurement of the decay time-dependent CP-violating asymmetry in B-s(0) -> phi phi decays is presented, along with measurements of the T-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between B-s(0) -(B) over bar (0)(s) mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 3.0 fb(-1) collected with the LHCb detector, a signal yield of approximately 4000 B-s(0) -> phi phi decays is obtained. The CP-violating phase is measured to be phi(s) = -0.17 +/- 0.15(stat) +/- 0.03(syst) rad. The triple-product asymmetries are measured to be A(U) = -0.003…
Measurement of the directCP-violating parameterACPin the decayD+→K−π+π+
2014
We measure the direct CP-violating parameter A_CP for the decay of the charged charm meson, D+ -> K-pi+pi+ (and charge conjugate), using the full 10.4 fb-1 sample of ppbar collisions at sqrt(s) = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B -> D processes) using input from Monte Carlo simulation. We measure A_CP = [-0.16 +- 0.15 (stat.) +- 0.09 (syst.)]%, which is consistent with zer…
Measurement of the forward-backward asymmetry in the distribution of leptons intt¯events in thelepton+jetschannel
2014
We present measurements of the forward-backward asymmetry in the angular distribution of leptons from decays of top quarks and antiquarks produced in proton-antiproton collisions. We consider the final state containing a lepton and at least three jets. The entire sample of data collected by the D0 experiment during Run II of the Fermilab Tevatron Collider, corresponding to 9.7 inverse fb of integrated luminosity, is used. The asymmetry measured for reconstructed leptons is $A_{FB}^l = \big(2.9 \pm 2.1(stat.) ^{+1.5}_{-1.7}(syst.) \big)$%. When corrected for efficiency and resolution effects within the lepton rapidity coverage of $|y_l|<1.5$, the asymmetry is found to be $A_{FB}^l = \big(4.2…
Measurement of the Top Quark Mass Using the Matrix Element Technique in Dilepton Final States
2016
We present a measurement of the top quark mass in ppbar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb-1. The matrix element technique is applied to ttbar events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton + jets final state of ttbar decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt = 173.93 +- 1.84 GeV.
Search for associated Higgs boson production using like charge dilepton events inpp¯collisions ats=1.96 TeV
2011
We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass o…
Study ofCP-violating charge asymmetries of single muons and like-sign dimuons inpp¯collisions
2014
We measure the inclusive single muon charge asymmetry and the like-sign dimuon charge asymmetry in $p \bar{p}$ collisions using the full data set of 10.4 fb$^{-1}$ collected with the D0 detector at the Fermilab Tevatron. The standard model predictions of the charge asymmetries induced by CP violation are small in magnitude compared to the current experimental precision, so non-zero measurements could indicate new sources of CP violation. The measurements differ from the standard model predictions of CP violation in these asymmetries with a significance of 3.6 standard deviations. These results are interpreted in a framework of $B$ meson mixing within the CKM formalism to measure the relativ…
Measurement of the W+b-jet and W+c-jet differential production cross sections in pp¯ collisions at s=1.96 TeV
2015
We present a measurement of the cross sections for the associated production of a $W$ boson with at least one heavy quark jet, $b$ or $c$, in proton-antiproton collisions. Data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators.
Measurement of the asymmetry in angular distributions of leptons produced in dileptontt¯final states inpp¯collisions ats=1.96 TeV
2013
We present measurements of asymmetries in angular distributions of leptons produced in t (t) over bar events in proton-antiproton collisions at the Fermilab Tevatron Collider. We consider final states where the W-+/- bosons from top quark and antiquark decays both decay into l nu (l = e, mu) resulting in oppositely charged dilepton final states with accompanying jets. Using 9.7 fb(-1) of integrated luminosity collected with the D0 detector, we find the asymmetries in lepton pseudorapidity compatible with predictions based on the standard model.
First Observation ofD0−D¯0Oscillations inD0→K+π−π+π−Decays and Measurement of the Associated Coherence Parameters
2016
Charm meson oscillations are observed in a time-dependent analysis of the ratio of D0→K+π−π+π− to D0→K−π+π−π+ decay rates, using data corresponding to an integrated luminosity of 3.0fb−1 recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favoured amplitudes rK3πD and the product of the coherence factor RK3πD and a charm mixing parameter y′K3π. The constraints measured are rK3πD=(5.67±0.12)×10−2, which is the most precise determination to date, and RK3πD⋅y′K3π=(0.3±1.8)×10−3, which provides useful input for determinations of the CP-violating phase γ in B±→DK±,D→K∓π±π∓π± decays. The analysis also …
Search for Higgs boson production in trilepton and like-charge electron-muon final states with the D0 detector
2013
We present a search for Higgs bosons in multilepton final states in pp-bar collisions at sqrt(s)=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider, using the full Run II data set with integrated luminosities of up to 9.7 fb-1. The multilepton states considered are two electron plus muon, electron with two muons, muon with two hadronic tau leptons, and like-charge electron-muon pairs. These channels directly probe the HVV (V=W,Z) coupling of the Higgs boson in production and decay. The muon with two hadronic tau lepton channel is also sensitive to H to tau lepton pair decays. Upper limits at the 95% C.L on the rate of standard model Higgs boson production are derived i…
Precision measurement of the ratio of the Λb0 to B¯0 lifetimes
2014
The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion.…
Measurement of the resonant andCPcomponents inB¯0→J/ψπ+π−decays
2014
The resonant structure of the reaction (B) over bar (0) --> J/psi pi(+)pi(-) is studied using data from 3 fb(-1) of integrated luminosity collected by the LHCb experiment, one third at 7 TeV center-of-mass energy and the remainder at 8 TeV. The invariant mass of the pi(+)pi(-) pair and three decay angular distributions are used to determine the fractions of the resonant and nonresonant components. Six interfering pi(+)pi(-) states, rho(770), f(0)(500), f(2)(1270), rho(1450), omega(782) and rho(1700), are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative charge parity fractions of each of the resonant final states are det…
Search for Sneutrino Production ineμFinal States in5.3 fb−1ofpp¯Collisions ats=1.96 TeV
2010
We report the results of a search for R parity violating (RPV) interactions leading to the production of supersymmetric sneutrinos decaying into emu final states using 5.3 fb^-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Having observed no evidence for production of emu resonances, we set direct bounds on the RPV couplings lambda^'_311 and lambda_312 as a function of sneutrino mass.
Measurement of spin correlation in ttbar production using a matrix element approach
2011
correlation, assuming that the spin of the top quark is either correlated with the spin of the anti-top quark as predicted by the standard model or is uncorrelated. For the first time we use a matrix-element-based approach to study ttbar spin correlation. We use {ttbar -> W+bW-bbar ->l+nubl-nub} final states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96 TeV, where l denotes an electron or a muon. The data correspond to an integrated luminosity of 5.4 fb-1 and were collected with the dzero detector at the Fermilab Tevatron collider. The result agrees with the standard model prediction. We exclude the hypothesis that the spins of the ttbar are uncorrelated at the …
Evidence for a Particle Produced in Association with Weak Bosons and Decaying to a Bottom-Antibottom Quark Pair in Higgs Boson Searches at the Tevatr…
2012
Aaltonen, T. et al.
Measurement of the relative branching ratio ofBs0→J/ψf0(980)toBs0→J/ψϕ
2012
We present a measurement of the relative branching fraction, R-f0/phi, of B-s(0) -> J/psi f(0)(980), with f(0)(980) -> pi(+)pi(-), to the process B-s(0) -> J/psi phi, with phi -> K+K-. The J/psi f(0)(980) final state corresponds to a CP-odd eigenstate of B-s(0) that could be of interest in future studies of CP violation. Using 8 fb(-1) of data recorded with the D0 detector at the Fermilab Tevatron Collider, we find R-f0/phi = 0.275 +/- 0.041(stat) +/- 0.061(syst).
Search for the rare decayBs0→μ+μ−
2013
Contains fulltext : 111249pub.pdf (Publisher’s version ) (Open Access) Contains fulltext : 111249.pdf (Author’s version preprint ) (Open Access)
Measurement of theB¯s0Meson Lifetime inDs+π−Decays
2014
The first measurement of the effective lifetime of the (B) over bar (o)(s) meson in the decay (B) over bar (o)(s) -> D-s(-) D-s(+) is reported using a proton-proton collision data set, corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment. The measured value of the (B) over bar (o)(s) -> D-s(-) D-s(+) effective lifetime is 1.379 +/- 0.026 +/- 0.017 ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light (B) over bar (o)(s) mass eigenstate of Gamma(L) 0.725 +/- 0.014 +/- 0.009 ps(-1). The (B) over bar (o)(s) lifetime is also measured using the flavor-specific (B) ov…
Combination of Tevatron searches for the standard model Higgs boson in the W+W- decay mode.
2010
11 páginas, 4 figuras, 1 tabla.-- CDF Collaboration: et al.
Search for Hidden-Sector Bosons inB0→K*0μ+μ−Decays
2015
A search is presented for hidden-sector bosons, $\chi$, produced in the decay ${B^0\!\to K^*(892)^0\chi}$, with $K^*(892)^0\!\to K^{+}\pi^{-}$ and $\chi\!\to\mu^+\mu^-$. The search is performed using $pp$-collision data corresponding to 3.0 fb$^{-1}$ collected with the LHCb detector. No significant signal is observed in the accessible mass range $214 \leq m({\chi}) \leq 4350$ MeV, and upper limits are placed on the branching fraction product $\mathcal{B}(B^0\!\to K^*(892)^0\chi)\times\mathcal{B}(\chi\!\to\mu^+\mu^-)$ as a function of the mass and lifetime of the $\chi$ boson. These limits are of the order of $10^{-9}$ for $\chi$ lifetimes less than 100 ps over most of the $m(\chi)$ range, a…
Measurement of the photon+b-jet production differential cross section in pp¯ collisions at s=1.96 TeV
2012
We present measurements of the differential cross section d sigma/dp(T)(gamma) for the inclusive production of a photon in association with a b-quark jet for photons with rapidities vertical bar y(gamma)vertical bar 15 GeV and rapidity vertical bar Y-jet vertical bar ) Collider at root s = 1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the k(T)-factorization QCD approach, and those from the SHERPA and PYTHIA Monte Carlo event generators.
Measurement of theZZproduction cross section and search for the standard model Higgs boson in the four lepton final state inpp¯collisions
2013
We present a measurement of Z boson pair production in p (p) over bar collisions at 1.96 TeV with 9.6 to 9.8 fb(-1) of D0 data. We examine the final states eeee, ee mu mu, and mu mu mu mu. Based on selected data, the measured cross section in the mass region M(Z/gamma*) > 30 GeV is sigma(p (p) over bar -> Z/gamma*Z/gamma*) = 1.26(-0.36)(+0.44)(stat)(-0.15)(+0.17) X (syst) +/- 0.08 (lumi) pb; after correcting for the expected ratio of sigma (p (p) over bar -> Z/gamma*Z/gamma*) to sigma(p (p) over bar -> ZZ), we derive a cross section for p (p) over bar -> ZZ production of 1.05(-0.30)(+0.37)(stat)(-0.12)(0.14)(syst) +/- 0.06 (lumi) pb. This result is combined with a previous result from the Z…
Search for the rare decay Bs 0→μ+μ-
2010
We present the results of a search for the flavor changing neutral current decay B-s(0) -> mu(+)mu(-) using 6.1 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of B-s(0) candidates is consistent with background expectations. The resulting upper limit on the branching fraction is B(B-s(0) -> mu(+)mu(-)) < 5.1 x 10(-8) at the 95% C.L. This limit is a factor of 2.4 better than that of the previous DO analysis and the best limit to date. Published by Elsevier B.V.
Measurement ofBc+Production in Proton-Proton Collisions ats=8 TeV
2015
Production of B+c mesons in proton-proton collisions at a center-of-mass energy of 8~TeV is studied with data corresponding to an integrated luminosity of 2.0 fb−1 recorded by the LHCb experiment. The ratio of production cross-sections times branching fractions between the B+c→J/ψπ+ and B+→J/ψK+ decays is measured as a function of transverse momentum and rapidity in the regions 0<pT<20 GeV/c and 2.0<y<4.5. The ratio integrated within this kinematic range is measured to be (0.683±0.018±0.009)%, where the first uncertainty is statistical and the second systematic.
Electron and Photon Identification in the D0 Experiment
2013
The electron and photon reconstruction and identification algorithms used by the D0 Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized.
First Observation of Top Quark Production in the Forward Region
2015
Top quark production in the forward region in proton-proton collisions is observed for the first time. The W + b final state with W → μν is reconstructed using muons with a transverse momentum, p[subscript T], larger than 25 GeV in the pseudorapidity range 2.0 20 GeV. The results are based on data corresponding to integrated luminosities of 1.0 and 2.0 fb[superscript -1] collected at center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross sections in the fiducial region are σ(top)[7 TeV] = 239 ± 53(stat) ± 33(syst) ± 24(theory) fb, σ(top)[8 TeV] = 289 ± 43(stat) ± 40(syst) ± 29(theory) fb.These results, along with the observed differential yields and c…
Study of Beauty Hadron Decays into Pairs of Charm Hadrons
2014
First observations of the decays Λ[0 over b] → Λ[+ over c]D[− over (s)] are reported using data corresponding to an integrated luminosity of 3 fb[superscript −1] collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(B[0 over s] → D[superscript +]D[− over s]) is made and a search is performed for the decays B[0 over (s)] → Λ[+ over c]Λ[− over c]. The results obtained are B(Λ[0 over b] → Λ[+ over c]D[superscript −])/B(Λ[0 over b] → Λ[+ over c]D[− over s]) = 0.042 ± 0.003(stat) ± 0.003(syst), ⎡⎣B(Λ[0 over b] → Λ[+ over c]D[− over s]) over B([¯ over B[superscript 0] → D[superscr…
Measurement of the ratio of differential cross sectionsσ(pp¯→Z+b jet)/σ(pp¯→Z+jet)inpp¯collisions ats=1.96 TeV
2013
We measure the ratio of cross sections, sigma(p (p) over bar -> Z + b jet)/sigma(p (p) over bar -> Z + jet), for associated production of a Z boson with at least one jet. The ratio is also measured as a function of the Z boson transverse momentum, jet transverse momentum, jet pseudorapidity, and the azimuthal angle between the Z boson with respect to the highest p(T) b tagged jet. These measurements use data collected by the D0 experiment in Run II of Fermilab's Tevatron p (p) over bar Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of 9.7 fb(-1). The results are compared to predictions from next-to-leading order calculations and various Monte Car…
Evidence for an anomalous like-sign dimuon charge asymmetry
2010
We measure the charge asymmetry $A\equiv(N^{++} - N^{--})/(N^{++} + N^{--})$ of like-sign dimuon events in 6.1~fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s}=1.96$~TeV at the Fermilab Tevatron collider. From $A$ we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb=-0.00957\pm0.00251\thinspace({\rm stat})\pm0.00146\thinspace({\rm sys})$. It differs by 3.2~standard deviations from the standard model prediction $\aslb({\rm SM})=(-2.3^{+0.5}_{-0.6})\times10^{-4}$, and provides first evidence of anomalous $CP$ violation in the mixing of neutral $B$ mesons.
Precision measurement of D meson mass differences
2013
Using three- and four-body decays of D mesons produced in semileptonic b-hadron decays, precision measurements of D meson mass differences are made together with a measurement of the D-0 mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1.0 fb(-1) collected in pp collisions at 7 TeV. Using the decay D-0 -> K+K-K-pi(+), the D-0 mass is measured to be M(D-0) = 1864.75 +/- 0.15 (stat) +/- 0.11 (syst) MeV/c(2). The mass differences M(D+) - M(D-0) = 4.76 +/- 0.12 (stat) +/- 0.07 (syst) MeV/c(2), M(D-s(+)) - M(D+) = 98.68 +/- 0.03 (stat) +/- 0.04 (syst) MeV/c(2) are measured using the D-0 -> K+K-pi(+)pi(-) and D-(s)(+) -> K+K-pi(+) modes.
Search for Doubly Charged Higgs Boson Pair Production inpp¯Collisions ats=1.96 TeV
2012
We present a search for pair production of doubly charged Higgs bosons in the processes $q\overline{q}\ensuremath{\rightarrow}{H}^{++}{H}^{--}$ decaying through ${H}^{\ifmmode\pm\else\textpm\fi{}\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}},{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}},{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}$. The search is performed in $p\overline{p}$ collisions at a center-of-mass energy of $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ using an integrated l…
Constraints on Models for the Higgs Boson with Exotic Spin and Parity inVH→Vbb¯Final States
2014
We present constraints on models containing non-standard-model values for the spin J and parity P of the Higgs boson H in up to 9.7 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. These are the first studies of Higgs boson J(P) with fermions in the final state. In the ZH -> llb (b) over bar, WH -> l nu b (b) over barb, and ZH -> nu nu b (b) over bar final states, we compare the standard model (SM) Higgs boson prediction, J(P) = 0(+), with two alternative hypotheses, J(P) = 0(-) and J(P) = 2(+). We use a likelihood ratio to quantify the degree to which our data are incompatible with non-SM J(P) predictions for a range…
Measurement oftt¯production in theτ+jetstopology usingpp¯collisions ats=1.96 TeV
2010
We present a measurement of the t (t) over bar production cross section multiplied by the branching ratio to tau lepton decaying semihadronically (tau(h)) plus jets, sigma(p (p) over bar -> t (t) over bar + X) center dot BR(t (t) over bar -> tau(h) + jets), at a center of mass energy root s = 1.96 TeV using 1 fb(-1) of integrated luminosity collected with the D0 detector. Assuming a top quark mass of 170 GeV, we measure sigma(t (t) over bar) center dot BR tau h (+ j) = 0.60(-0.22)(+0.23)(stat)(-0.14)(+0.15)(syst) +/- 0.04(lumi) pb. In addition, we extract the t (t) over bar production cross section using the t (t) over bar -> tau(h) + jets topology, with the result sigma(t (t) over bar) = 6…
Measurement of the DirectCP-violating Charge Asymmetry inDs±→ϕπ±Decays
2014
We present a measurement of the direct CP-violating charge asymmetry in Ds+ → ϕ π(±) decays where the ϕ meson decays to K(+)K(-), using the full Run II data set with an integrated luminosity of 10.4 fb-1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. The normalized difference A(CP) in the yield of D(s)(+) and D(s)(-) mesons in these decays is measured by fitting the difference between their reconstructed invariant mass distributions. This results in an asymmetry of A(CP) = [-0.38 ± 0.27]%, which is the most precise measurement of this quantity to date. The result is consistent with the standard model prediction of zero CP asymmetry in thi…
Study of W Boson Production in Association with Beauty and Charm
2015
The associated production of a W boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and 2.0 fb[superscript -1] collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The W bosons are reconstructed using the W → μν decay and muons with a transverse momentum, p[subscript T], larger than 20 GeV in the pseudorapidity range 2.0 20 GeV and 2.2 20 GeV. The fraction of W + jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the W + b and W + c produ…
Measurement of the chi(b) (3 P) mass and of the relative rate of chi(b1) (1 P) and chi(b2) (1 P) production
2014
The production of $\chi_b$ mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of $\sqrt{s}=7$ and $8$ TeV and corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $\chi_b$ mesons are identified through their decays to $\Upsilon(1S)\gamma$ and $\Upsilon(2S)\gamma$ using photons that converted to $e^+e^-$ pairs in the detector. The $\chi_b(3P)$ meson mass, and the relative prompt production rate of $\chi_{b1}(1P)$ and $\chi_{b2}(1P)$ mesons as a function of the $\Upsilon(1S)$ transverse momentum in the $\chi_b$ rapidity range 2.0< $y$<4.5, are measured. Assuming a mass splitting between the $\chi_{b1}(3P)$ an…
Measurement of the t-channel single top quark production cross section
2009
The D0 collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for the t-channel and 1.05 +…
Precision measurement of the top-quark mass inlepton+jetsfinal states
2015
We measure the mass of the top quark in lepton + jets final states using the full sample of p (p) over bar collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at root s = 1.96 TeV, corresponding to 9.7 fb(-1) of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from t (t) over bar production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure m(t) = 174.98 +/- 0.76 GeV. This constitutes the most precise single measurement of the top-quark mass.
An improved determination of the width of the top quark
2012
We present an improved determination of the total width of the top quark, $\Gamma_t$, using 5.4 fb$^{-1}$ of integrated luminosity collected by the D0 Collaboration at the Tevatron $p\bar{p}$ Collider. The total width $\Gamma_t$ is extracted from the partial decay width $\Gamma(t\to Wb)$ and the branching fraction $\mathcal{B}(t\to Wb)$. $\Gamma(t\to Wb)$ is obtained from the $t$-channel single top quark production cross section and $\mathcal{B}(t\to Wb)$ is measured in $t\bar{t}$ events. For a top mass of $172.5\;\rm GeV$, the resulting width is $\Gamma_t = 2.00^{+0.47}_{-0.43}$ GeV. This translates to a top-quark lifetime of $\tau_t = (3.29^{+0.90}_{-0.63})\times10^{-25}$ s. We also extra…
Observation of charmonium pairs produced exclusively in $pp$ collisions
2014
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measu…
Search for the Associated Production of abQuark and a Neutral Supersymmetric Higgs Boson that Decays intoτPairs
2010
We report results from a search for production of a neutral Higgs boson in association with a $b$ quark. We search for Higgs decays to $\tau$ pairs with one $\tau$ subsequently decaying to a muon and the other to hadrons. The data correspond to 2.7fb$^{-1}$ of $\ppbar$ collisions recorded by the D0 detector at $\sqrt{s} = 1.96$TeV. The data are found to be consistent with background predictions. The result allows us to exclude a significant region of parameter space of the minimal supersymmetric model.
Combined Search for the Standard Model Higgs Boson Decaying tobb¯Using the D0 Run II Data Set
2012
We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into b bbar using the data sample collected with the D0 detector in p pbar collisions at sqrt{s}=1.96 TeV at the Fermilab Tevatron Collider. We derive 95% CL upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV <= M_H <= 150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% CL. In the mass range 120 GeV <= M_H <= 145 GeV the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectat…
Precision luminosity measurements at LHCb
2014
Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy $\sqrt{s}$. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for $\sqrt{s}$ = 2.76, 7 and 8 TeV (proton-proton collisions) and for $\sqrt{s_{NN}}$ = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves sig…
Measurement of the ratio of inclusive cross sectionsσ(pp¯→Z+2b jets /σ(pp¯→Z+2 jets)inpp¯collisions ats=1.96 TeV
2015
In this study, we measure the ratio of cross sections, σ(pp¯ → Z + 2 b jets)/σ(pp¯ → Z + 2 jets), for associated production of a Z boson with at least two jets with transverse momentum pjetT > 20 GeV and pseudorapidity |ηjet| < 2.5. This measurement uses data corresponding to an integrated luminosity of 9.7 fb–1 collected by the D0 experiment in Run II of Fermilab’s Tevatron pp¯ Collider at a center-of-mass energy of 1.96 TeV. The measured integrated ratio of 0.0236 ± 0.0032(stat) ± 0.0035(syst) is in agreement with predictions from next-to-leading-order perturbative QCD and the Monte Carlo event generators PYTHIA and ALPGEN.
Dalitz plot analysis ofBs0→D¯0K−π+decays
2014
The resonant substructure of B-s(0) -> (D) over bar K-0(-)pi(+) decays is studied with the Dalitz plot analysis technique. The study is based on a data sample corresponding to an integrated luminosity of 3.0 fb(-1) of pp collision data recorded by LHCb. A structure at m((D) over bar K-0(-)) approximate to 2.86 GeV/c(2) is found to be an admixture of spin-1 and spin-3 resonances. The masses and widths of these states and of the D-s2*(2573)(-) meson are measured, as are the complex amplitudes and fit fractions for all the (D) over bar K-0(-) and K-pi(-) components included in the amplitude model. In addition, the D-s2*(2573)(-) resonance is confirmed to be spin 2.
Measurement of the differential γ+c-jet cross section and the ratio of differential γ+c and γ+b cross sections in pp¯ collisions at s=1.96 TeV
2013
We present measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^{\gamma}| 15$ GeV. The cross section ratios $\sigma(\gamma+c)/\sigma(\gamma+b)$ as a function of $p_{T}^{\gamma}$ are also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=$1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the $k_{T}$-factorization approach, and to pr…
Measurements of single top quark production cross sections and|Vtb|inpp¯collisions ats=1.96 TeV
2011
We present measurements of production cross sections of single top quarks in $\ppbar$ collisions at $\sqrt{s}=1.96\;\rm TeV$ in a data sample corresponding to an integrated luminosity of $5.4\;\rm fb^{-1}$ collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of $\sigma({\ppbar}{\rargap}tb+X, tqb+X) = 3.43\pm^{0.73}_{0.74}\;\rm pb$ and use it to extract the CKM matrix element $0.79 < |V_{tb}| \leq 1$ at the 95% C.L. We also measure $\sigma({\ppbar}{\rargap}tb+X) = 0.68\pm^{0.38}…
Measurement of CP asymmetry in D 0 → K - K + and D 0 → π - πdecays
2014
Time-integrated $CP$ asymmetries in $D^0$ decays to the final states $K^- K^+$ and $\pi^- \pi^+$ are measured using proton-proton collisions corresponding to $3\mathrm{\,fb}^{-1}$ of integrated luminosity collected at centre-of-mass energies of $7\mathrm{\,Te\kern -0.1em V}$ and $8\mathrm{\,Te\kern -0.1em V}$. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in $CP$ asymmetries between the two final states is measured to be \begin{align} \Delta A_{CP} = A_{CP}(K^-K^+)-A_{CP}(\pi^-\pi^+) = (+0.14 \pm 0.16\mathrm{\,(stat)} \pm 0.08\mathrm{\,(syst)})\% \ . \nonu…
Observation of charmless baryonic decays B(s)0→pp¯h+h′−
2017
Decays of B0 and Bs0 mesons to the charmless baryonic final states pp¯h+h′-, where h and h′ each denote a kaon or a pion, are searched for using the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. Four-body charmless baryonic Bs0 decays are observed for the first time. The decays Bs0→pp¯K+K-, Bs0→pp¯K±π∓, B0→pp¯K±π∓ and B0→pp¯π+π- are observed with a significance greater than 5 standard deviations; evidence at 4.1 standard deviations is found for the B0→pp¯K+K- decay and an upper limit is set on the branching fraction for Bs0→pp¯π+π-. Branching fraction…
Observation of s-Channel Production of Single Top Quarks at the Tevatron
2014
We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7fb-1 per experiment. The measured cross section is σs=1.29-0.24+0.26pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8×10-10, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks. © 2014 American Physical Society.
Measurement of CP asymmetry in Bs0 → Ds ∓K± decays
2014
Journal of high energy physics 2018(3), 59 (2018). doi:10.1007/JHEP03(2018)059
Measurement of the $W$ boson mass with the D0 detector
2012
We give a detailed description of the measurement of the $W$ boson mass, $M_W$, performed on an integrated luminosity of 4.3 fb$^{-1}$, which is based on similar techniques as used for our previous measurement done on an independent data set of 1 fb$^{-1}$ of data. The data were collected using the D0 detector at the Fermilab Tevatron Collider. This data set yields $1.68\times 10^6$ $W\rightarrow e\nu$ candidate events. We measure the mass using the transverse mass, electron transverse momentum, and missing transverse energy distributions. The $M_W$ measurements using the transverse mass and the electron transverse momentum distributions are the most precise of these three and are combined …
Measurement of the electron charge asymmetry inpp¯→W+X→eν+Xdecays inpp¯collisions ats=1.96 TeV
2015
We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the prot…
Search for Structure in theBs0π±Invariant Mass Spectrum
2016
The $B_s^0\pi^\pm$ invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to $3$ fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 7$ and $8$ TeV. No significant excess is found, and upper limits are set on the production rate of the claimed $X(5568)$ state. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the $B_s^0\pi^\pm$ final state.
Search for Neutral Higgs Bosons in Events with Multiple Bottom Quarks at the Tevatron
2012
The combination of searches performed by the CDF and D0 collaborations at the Fermilab Tevatron Collider for neutral Higgs bosons produced in association with b quarks is reported. The data, corresponding to 2.6fb -1 of integrated luminosity at CDF and 5.2fb -1 at D0, have been collected in final states containing three or more b jets. Upper limits are set on the cross section multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson. Significant enhancements to the production of Higgs bosons can be found in theories beyond the standard model, for example, in supersymmetry. The results are int…
Study of the decayBs0→J/ψf2′(1525)inμ+μ−K+K−final states
2012
We investigate the decay $B_s^0 \rightarrow J/\psi K^+ K^-$ for invariant masses of the $K^+K^-$ pair in the range $1.35
Evidence for Zc±(3900) in semi-inclusive decays of b -flavored hadrons
2018
We present evidence for the exotic charged charmoniumlike state Zc±(3900) decaying to J/ψπ± in semi-inclusive weak decays of b-flavored hadrons. The signal is correlated with a parent J/ψπ+π- system in the invariant-mass range 4.2-4.7 GeV that would include the exotic structure Y(4260). The study is based on 10.4 fb-1 of pp collision data collected by the D0 experiment at the Fermilab Tevatron collider. © 2018 authors. Published by the American Physical Society.
Dependence of the tt¯ production cross section on the transverse momentum of the top quark
2010
We present a measurement of the differential cross section for $t\bar{t}$ events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV as a function of the transverse momentum ($p_T$) of the top quark. The selected events contain a high-$p_T$ lepton ($\ell$), four or more jets, and a large imbalance in $p_T$, and correspond to 1 fb${}^{-1}$ of integrated luminosity recorded with the D0 detector. Each event must have at least one candidate for a $b$ jet. Objects in the event are associated through a constrained kinematic fit to the $t\bar{t}\to WbW\bar{b} \to \ell\nu b q\bar{q}'\bar{b}$ process. Results from next-to-leading-order perturbative QCD calculations agree with the measured diffe…
Measurement of color flow intt¯events frompp¯collisions ats=1.96 TeV
2011
We present the first measurement of the color representation of the hadronically decaying W boson in t-tbar events, from 5.3 fb^-1 of integrated luminosity collected with the D0 experiment. A novel calorimeter-based vectorial variable, "jet pull," is used, sensitive to the color-flow structure of the final state. We find that the fraction of uncolored W bosons is 0.56 +- 0.42(stat+syst), in agreement with the standard model.
Measurements of inclusive W+jets production rates as a function of jet transverse momentum in pp¯ collisions at s=1.96 TeV
2011
This Letter describes measurements of inclusive W (--> e nu) + n jet cross sections (n = 1-4), presented as total inclusive cross sections and differentially in the nth jet transverse momentum. The measurements are made using data corresponding to an integrated luminosity of 4.2 fb-1 collected by the D0 detector at the Fermilab Tevatron Collider, and achieve considerably smaller uncertainties on W +jets production cross sections than previous measurements. The measurements are compared to next-to-leading order perturbative QCD (pQCD) calculations in the n =1-3 jet multiplicity bins and to leading order pQCD calculations in the 4-jet bin. The measurements are generally in agreement with pQCD…
Search forZγevents with large missing transverse energy inpp¯collisions ats=1.96 TeV
2012
We present the first search for new phenomena in Z gamma final states with large missing transverse energy using data corresponding to an integrated luminosity of 6.2 fb(-1) collected with the D0 experiment in p (p) over bar collisions at root s 1.96 TeV. This signature is predicted in gauge-mediated supersymmetry-breaking models, where the lightest neutralino (chi) over tilde (0)(1) is the next-to-lightest supersymmetric particle and is produced in pairs, possibly through decay from heavier supersymmetric particles. The (chi) over tilde (0)(1) can decay either to a Z boson or a photon and an associated gravitino that escapes detection. We exclude this model at the 95% C.L. for supersymmetr…
Measurement of the top-quark mass inpp¯collisions using events with two leptons
2012
Made available in DSpace on 2022-04-29T05:11:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-09-26 We present a measurement of the top-quark mass (m t) in pp̄ collisions at √s=1.96TeV using tt̄ events with two leptons (ee, eμ, or μμ) and accompanying jets in 4.3fb -1 of data collected with the D0 detector at the Fermilab Tevatron collider. We analyze the kinematically underconstrained dilepton events by integrating over their neutrino rapidity distributions. We reduce the dominant systematic uncertainties from the calibration of jet energy using a correction obtained from tt̄ events with a final state of a single lepton plus jets. We also correct jets in simulated events to replic…
First observation and amplitude analysis of theB−→D+K−π−decay
2015
The B- -> D+K-pi(-) decay is observed in a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. Its branching fraction is measured to be B(B- -> D+K-pi(-)) = (7.31 +/- 0.19 +/- 0.22 +/- 0.39) x 10(-5) where the uncertainties are statistical, systematic and from the branching fraction of the normalization channel B- -> D+pi(-)pi(-), respectively. An amplitude analysis of the resonant structure of the B- -> D+K-pi(-) decay is used to measure the contributions from quasi-two-body B- -> D-0* (2400)K-0(-), B- -> D-2* (2460)K-0(-), and B- -> D-J* (2760)K-0(-) decays, as well as from nonresonant sources. The D-J* (2760)(0) resonance is …
Measurement of the differential cross section of photon plus jet production inpp¯collisions ats=1.96 TeV
2013
We study the process of associated photon and jet production, p (p) over bar -> gamma + jet + X, using 8.7 fb(-1) of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy root s = 1.96 TeV. Photons are reconstructed with rapidity vertical bar y(gamma)vertical bar 20 GeV. The highest-p(T) jet is required to be in one of four rapidity regions up to vertical bar y(jet)vertical bar 0) and opposite signs (y(gamma)y(jet) <= 0) of photon and jet rapidities. We compare the measured triple-differential cross sections, d(3)sigma/dp(T)(gamma)dy(gamma)dy(jet), to next-to-leading order (NLO) perturbative QCD calculations using different sets of p…
Measurement of the lifetime of theBc+meson using theBc+→J/ψπ+decay mode
2015
The difference in total widths between the B+c and B+ mesons is measured using 3.0fb−1 of data collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of B+c→J/ψπ+ and B+→J/ψK+ decays, the width difference is measured to beΔΓ≡ΓB+c−ΓB+=4.46±0.14±0.07mm−1c,where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B+c lifetime,τB+c=513.4±11.0±5.7fs,where the first uncertainty is statistical and the second systematic.
Measurement of the SemileptonicCPAsymmetry inB0-B¯0Mixing
2015
The semileptonic $CP$ asymmetry in $B^0-\overline{B}{}^0$ mixing, $a_{\rm sl}^d$, is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb experiment. Semileptonic $B^0$ decays are reconstructed in the inclusive final states $D^-\mu^+$ and $D^{*-}\mu^+$, where the $D^-$ meson decays into the $K^+\pi^-\pi^-$ final state, and the $D^{*-}$ meson into the $\overline{D}{}^0(\rightarrow K^+\pi^-)\pi^-$ final state. The asymmetry between the numbers of $D^{(*)-}\mu^+$ and $D^{(*)+}\mu^-$ decays is measured as a function of the decay time of the $B^0$ mesons. The $CP$ asymmetry is measured to be $a_{\rm sl}^d = (-0.02 \pm 0.19 \pm…
Measurement of theΛb0lifetime in the exclusive decayΛb0→J/ψΛ0inpp¯collisions ats=1.96 TeV
2012
We measure the Lambda_b^0 lifetime in the fully reconstructed decay Lambda_b^0 -> J/psi Lambda^0 using 10.4 fb^-1 of ppbar collisions collected with the D0 detector at sqrt(s)=1.96 TeV. The lifetime of the topologically similar decay channel B^0 -> J/psi K^0_S is also measured. We obtain tau(Lambda_b^0) = 1.303 +- 0.075 (stat.) +- 0.035 (syst.) ps and tau(B^0) = 1.508 +- 0.025 (stat.) +- 0.043 (syst.) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda_b^0)/tau(B^0) = 0.864 +- 0.052 (stat.) +- 0.033 (syst.).
Measurement ofCPviolation parameters inB0→DK*0decays
2014
An analysis of B0→DK*0 decays is presented, where D represents an admixture of D0 and D¯0 mesons reconstructed in four separate final states: K−π+, π−K+, K+K− and π+π−. The data sample corresponds to 3.0 fb−1 of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of rB(DK*0), the magnitude of the ratio of the amplitudes of the decay B0→DK+π− with a b→u or a b→c transition, in a Kπ mass region of ±50 MeV/c2 around the K∗(892) mass and for an absolute value of the cosine of the K*0 helicity angle larger than 0.4.
Search for CP violation inD0→π−π+π0decays with the energy test
2015
A search for time-integrated CP violation in the Cabibbo-suppressed decay D-0 -> pi(-)pi(+)pi(0) ir is performed using for the first time an unbinned model-independent technique known as the energy test. Using proton-proton collision data, corresponding to an integrated luminosity of 2.0 fb(-1) collected by the LHCb detector at a centre-of-mass energy of root s = 8 TeV, the world's best sensitivity to CP violation in this decay is obtained. The data are found to be consistent with the hypothesis of CP symmetry with a p-value of (2.6 +/- 0.5)%. (C) 2014 The Authors. Published by Elsevier B.V.
Observation of $Z$ production in proton-lead collisions at LHCb
2014
The first observation of $Z$ boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of $\sqrt{s_{NN}}=5~\text{TeV}$ is presented. The data sample corresponds to an integrated luminosity of $1.6~\text{nb}^{-1}$ collected with the LHCb detector. The $Z$ candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above $20~\text{GeV}/c$. The invariant dimuon mass is restricted to the range $60-120~\text{GeV}/c^2$. The $Z$ production cross-section is measured to be \begin{eqnarray*} ��_{Z\to��^+��^-}(\text{fwd})&=&13.5^{+5.4}_{-4.0}\text{(stat.)}\pm1.2\text{(syst.)}~\text{nb} …
Search for pair production of the scalar top quark in the electron-muon final state
2010
We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ($\tilde{t}_1$) in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The scalar top quarks are assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tilde{\nu}$), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and improved exclusion limits at the 95% C.L. are set in the the ($M_{\tilde{t}_1}$,$M_{\tilde{\nu}}$) mass plane.
Evidence for Exotic Hadron Contributions toΛb0→J/ψpπ−Decays
2016
A full amplitude analysis of $\Lambda_b^0 \to J/\psi p \pi^-$ decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations $N\to p\pi^-$, either the $P_c(4380)^+$ and $P_c(4450)^+\to J/\psi p$ states, previously observed in $\Lambda_b^0 \to J/\psi p K^-$ decays, or the $Z_c(4200)^-\to J/\psi \pi^-$ state, previously reported in $B^0 \to J/\psi K^+ \pi^-$ decays, or all three, are included in the amplitude models. The data support a model containing all three exotic sta…
Search for Higgs bosons decaying to τ+τ− pairs in pp¯ collisions at s=1.96 TeV
2012
Abstract We present a search for the production of neutral Higgs bosons decaying into τ + τ − pairs in p p ¯ collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb−1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into τ + τ − pairs, and we interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.
Combination of CDF and D0 W-Boson mass measurements
2013
We summarize and combine direct measurements of the mass of the W boson in √s=1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb-1 of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb-1 of integrated luminosity. The resulting Tevatron average for the mass of the W boson is M W=80387±16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of M W…
Improved $b$ quark jet identification at the D0 experiment
2013
The ability to identify jets which originated from $b$ quarks is an important tool of the physics program of the D0 experiment at the Fermilab Tevatron $p\bar{p}$ collider. This article describes a new algorithm designed to select jets originating from $b$ quarks while suppressing the contamination caused by jets from other quark flavors and gluons. Additionally, a new technique, the SystemN method, for determining the misidentification rate directly from data is presented.
Measurement of the combined rapidity and pT dependence of dijet azimuthal decorrelations in pp¯ collisions at s=1.96 TeV
2013
We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, using the recently proposed quantity R-Delta phi. The variable R-Delta phi measures the fraction of the inclusive dijet events in which the azimuthal separation of the two jets with the highest transverse momenta is less than a specified value of the parameter Delta phi(max). The quantity R-Delta phi is measured in p (p) over bar collisions at root s = 1.96 TeV, as a function of the dijet rapidity interval, the total scalar transverse momentum, and Delta phi(max). The measurement uses an event sample corresponding to an integrated luminosity of 0.7 fb(-1) collected…
Search for the Standard Model Higgs Boson in theH→WW→lνq′q¯Decay Channel
2011
We present a search for the standard model Higgs boson (H) in ppbar collisions at sqrt{s}=1.96 TeV in events containing a charged lepton (ell), missing transverse energy, and at least two jets, using 5.4 fb^-1 of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H->WW->ell+nu+q'qbar, where ell is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH->ell+nu+bbbar In the absence of signal, we set limits at the 95% C.L. on the cross section for H production si…
Observation and studies of double J/psi production at the Tevatron
2014
We present the observation of doubly-produced $J/\psi$ mesons with the D0 detector at Fermilab in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV. The production cross section for both singly and doubly-produced $J/\psi$ mesons is measured using a sample with an integrated luminosity of 8.1fb$^{-1}$. For the first time, the double $J/\psi$ production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section $\sigma_{eff}$, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.
Differential branching fractions and isospin asymmetries of B -> K ((*)) μ(+) μ(-) decays
2014
The isospin asymmetries of $B \to K\mu^+\mu^-$ and $B \to K^{*}\mu^+\mu^-$ decays and the partial branching fractions of the $B^0 \to K^0\mu^+\mu^-$, $B^+ \to K^+\mu^+\mu^-$ and $B^+ \to K^{*+}\mu^+\mu^-$ decays are measured as functions of the dimuon mass squared, $q^2$. The data used correspond to an integrated luminosity of 3$~$fb$^{-1}$ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7$\,$TeV and 8$\,$TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions, while individually consistent, all favour lower values than their respective Standard M…
Measurement of the semileptonic charge asymmetry in B-0 meson mixing with the D0 detector
2012
We present a measurement of the semileptonic mixing asymmetry for B0 mesons, a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- -> K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1} of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at the Fermilab Tevatron collider. We extract the charge asymmetries in these two channels as a function of the visible proper decay length (VPDL) of the B0 meson, correct for detector-related asymmetries using data-driven methods, and account for dilution from charge-symmetric processes using Monte Car…
Measurement of the electric charge of the top quark intt¯events
2014
We present a measurement of the electric charge of top quarks using t (t) over bar events produced in p (p) over bar collisions at the Tevatron. The analysis is based on fully reconstructed t (t) over bar pairs in lepton + jets final states. Using data corresponding to 5.3 fb(-1) of integrated luminosity, we exclude the hypothesis that the top quark has a charge of Q = -4/3e at a significance greater than 5 standard deviations. We also place an upper limit of 0.46 on the fraction of such quarks that can be present in an admixture with the standard model top quarks (Q = +2/3e) at a 95% confidence level.
Measurement of resonant andCPcomponents inB¯s0→J/ψπ+π−decays
2014
Structure of the decay Bs0→J/ψπ+π- is studied using data corresponding to 3fb-1 of integrated luminosity from pp collisions produced by the LHC and collected by the LHCb detector. Five interfering π+π- states are required to describe the decay: f0(980),f0(1500),f0(1790),f2(1270), and f2′(1525). An alternative model including these states and a nonresonant J/ψπ+π- component also provides a good description of the data. Based on the different transversity components measured for the spin-2 intermediate states, the final state is found to be compatible with being entirely CP odd. The CP-even part is found to be <2.3% at a 95% confidence level. The f0(500) state is not observed, allowing a limi…
Study of the rare Bs0 and B0 decays into the π+π−μ+μ− final state
2015
A search for the rare decays B0s→π+π−μ+μ− and B0→π+π−μ+μ− is performed in a data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0s→π+π−μ+μ− and the first evidence of the decay B0→π+π−μ+μ− are obtained and the branching fractions are measured to be B(B0s→π+π−μ+μ−)=(8.6±1.5(stat)±0.7(syst)±0.7(norm))×10−8 and B(B0→π+π−μ+μ−)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))×10−8, where the third unc…
Precision Measurement of the Top Quark Mass in <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="in…
2014
We measure the mass of the top quark in lepton$+$jets final states using the full sample of $$p\bar{p}$$ collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at $$\sqrt s=1.96 $$TeV, corresponding to $$9.7 {\rm fb}^{-1}$$ of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from $$t\bar t$$ production or background. The overall jet energy scale is constrained in situ by the mass of the $W$ boson. We measure $$m_t=174.98\pm0.76$$ GeV. In conclusion, this constitutes the most precise single measurement of the top-quark mass.
Search for Higgs boson production in oppositely charged dilepton and missing energy final states in9.7 fb−1ofpp¯collisions ats=1.96 TeV
2013
We present a search for Higgs boson in final states with two oppositely charged leptons and large missing transverse energy as expected in H -> WW -> lvlv decays. The events are selected from the full Run II data sample of 9.7 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider at sqrt s = 1.96 TeV. To validate our search methodology, we measure the non-resonant W W production cross section and find sigma_WW = 11.6 +/- 0.7 pb, in agreement with the standard model prediction. In the Higgs boson search, no significant excess above the background expectation is observed. Upper limits at the 95% confidence level on the Higgs boson production cross section a…
Observation ofJ/ψpResonances Consistent with Pentaquark States inΛb0→J/ψK−pDecays
2015
Observations of exotic structures in the J/ψp channel, that we refer to as pentaquark-charmonium states, in Λ0b→J/ψK−p decays are presented. The data sample corresponds to an integrated luminosity of 3/fb acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis is performed on the three-body final-state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29 MeV and a width of 205±1…
Inclusive Production of theX(4140)State inpp¯Collisions at D0
2015
We present a study of the inclusive production of the $X(4140)$ with the decay to the $J/\psi \phi$ final state in hadronic collisions. Based on $10.4~\rm{fb^{-1}}$ of $p \overline p $ collision data collected by the D0 experiment at the Fermilab Tevatron collider, we report the first evidence for the prompt production of $X(4140)$ and find the fraction of $X(4140)$ events originating from $b$ hadrons to be $f_b=0.39\pm 0.07 {\rm \thinspace (stat)} \pm 0.10 {\rm \thinspace (syst)} $. The ratio of the non-prompt $X(4140)$ production rate to the $B_s^0$ yield in the same channel is $R=0.19 \pm 0.05 {\rm \thinspace (stat)} \pm 0.07 {\rm \thinspace (syst)}$. The values of the mass $M=4152.5 \pm…
Measurement of differentialtt¯production cross sections inpp¯collisions
2014
The production of top quark-antiquark pair events in pp collisions at root s= 1.96 TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the tt pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a b quark. The data sample corresponds to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.
Search for a Fourth Generationt′Quark inpp¯Collisions ats=1.96 TeV
2011
We present a search for pair production of a fourth generation t' quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5.3/fb of proton-antiproton collisions at sqrt{s}=1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the t't'bar production cross section that exclude at the 95% C.L. a t' quark that decays exclusively to W+jet with a mass below 285 GeV. We observe a small excess in the muon+jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.
Combination of the top-quark mass measurements from the Tevatron collider
2012
Aaltonen, T. et al.
Combination of D0 measurements of the top quark mass
2017
We present a combination of measurements of the top quark mass by the D0 experiment in the lepton+jets and dilepton channels. We use all the data collected in Run I (1992--1996) at $\sqrt s=1.8$ TeV and Run II (2001--2011) at $\sqrt s=1.96$ TeV of the Tevatron $p \bar{p}$ collider, corresponding to integrated luminosities of 0.1 fb$^{-1}$ and 9.7 fb$^{-1}$, respectively. The combined result is: $m_t = 174.95 \pm0.40\,{\rm(stat)} \pm 0.64\,{\rm(syst)}\,{\rm{GeV}}=174.95 \pm 0.75 \, {\rm{GeV}}$.
WγProduction and Limits on AnomalousWWγCouplings inpp¯Collisions ats=1.96 TeV
2011
We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W -> lnu+gamma production in egamma and mugamma final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the cross section multiplied by the branching fraction for the process ppbar -> Wgamma+X -> lnugamma+X, measured to be 15.8 +/- 0.8 (stat.) +/- 1.2 (syst.) pb, and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WWgamma couplings for data from hadron coll…
Studies ofWboson plus jets production inpp¯collisions ats=1.96 TeV
2013
We present a comprehensive analysis of inclusive W(-> ev) + n-jet (n >= 1, 2, 3, 4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb(-1) data set collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (P-T) and pseudorapidity (eta), the scalar sum of the transverse energies of the W boson and all jets (H-T), leading dijet P-T and invariant mass, dijet rapidity separations for a variety of jet pairings for P-T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for P-T-ordered and angular-ordered j…
Evidence for Spin correlation in tt̄ production
2012
Made available in DSpace on 2022-04-29T03:09:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-19 We present a measurement of the ratio of events with correlated t and t̄ spins to the total number of tt̄ events. This ratio f is evaluated using a matrix-element-based approach in 729 tt̄ candidate events with a single lepton (electron or muon) and at least four jets. The analyzed pp̄ collisions data correspond to an integrated luminosity of 5.3fb -1 and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy √s=1.96TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the …
Search for flavor changing neutral currents in decays of top quarks
2011
We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for ttbar -> l'null + jets (l, l' = e, mu) final states using 4.1 fb^-1 of integrated luminosity of ppbar collisions at sqrt(s) = 1.96 TeV. We extract limits on the branching ratio B(t -> Zq) (q = u, c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B < 3.2% at 95% C.L.
Effective lifetime measurements in theBs0→K+K−,B0→K+π−andBs0→π+K−decays
2014
Measurements of the effective lifetimes in the B-s(0) -> K+K-, B-0 -> K+pi(-) and B-s(0) -> pi K-+(-) decays are presented using 1.0 fb(-1)of pp collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance. The measured effective lifetimes are tau(Bs0 -> K+K-) = 1.407 +/- 0.016 (stat) +/- 0.007 (syst) ps, tau(Bs0 -> K+pi-) = 1.524 +/- 0.011 (stat) +/- 0.004 (syst) ps, tau(Bs0 ->pi+K-) = 1.60 +/- 0.06 (stat) +/- 0.01 (syst) ps. This is the most precise determination to date of the effective lifetime in the B-s(0) -> K+K- decay and provides constraints on contributions from physics beyond…
Measurement of theBs0Lifetime in the Flavor-Specific Decay ChannelBs0→Ds−μ+νX
2015
We present an updated measurement of the B-s(0) lifetime using the semileptonic decays B-s(0) -> D-s(-)mu(+)nu X, with D-s(-) -> phi pi(-) and phi -> K+K- (and the charge conjugate process). This measurement uses the full Tevatron Run II sample of proton-antiproton collisions at root s = 1.96 TeV, comprising an integrated luminosity of 10.4 fb(-1). We find a flavor-specific lifetime tau(fs)(B-s(0)) = 1.479 +/- 0.010(stat) +/- 0.021(syst) ps. This technique is also used to determine the B-0 lifetime using the analogous B-0 -> D- mu(+)nu X decay with D- -> phi pi(-) and phi -> K+K-, yielding tau(B-0) = 1.534 +/- 0.019(stat) +/- 0.021(syst) ps. Both measurements are consistent with the current…
Measurement of spin correlation in tt¯ production using dilepton final states
2011
We measure the correlation between the spin of the top quark and the spin of the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and tbar rest frames, yielding a correlation strength C= 0.10^{+0.45}_{-0.45}, in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
Studies of the resonance structure inD0→KS0K±π∓decays
2016
Amplitude models are constructed to describe the resonance structure of D0→ K-π+π+π- and D0→ K+π-π-π+ decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb- 1. The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes D0→ a1(1260) +K- and D0→ K1(1270 / 1400) +π- being prominent in D0→ K-π+π+π- and D0→ K+π-π-π+, respectively. Precise measurements of the lineshape parameters and couplings of the a1(1260) +, K1(1270) - and K(1460) - resonances are made, and a quasi model-independent study of the K(1460) - resonance is performed. The coher…
Search for universal extra dimensions in ppbar collisions
2012
We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb$^{-1}$, collected by the D0 detector at a $p\bar p$ center of mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of $R^{-1}>260$ GeV in a minimal UED model.
Azimuthal decorrelations and multiple parton interactions inγ+2jet andγ+3jet events inpp¯collisions ats=1.96 TeV
2011
Samples of inclusive photon+2 jet and photon+3 jet events collected by the D0 experiment with an integrated luminosity of about 1fb^-1 in ppbar collisions at sqrt{s}=1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (pT) of the photon+leading jet system (jets are ordered in pT) and pT of the other jet for photon+2 jet, or pT sum of the two other jets for photon+3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and…
Zγproduction and limits on anomalousZZγandZγγcouplings inpp¯collisions ats=1.96 TeV
2012
We present a measurement of ppbar->Zgamma->ll+gamma (l = e, mu) production with a data sample corresponding to an integrated luminosity of 6.2 fb^{-1} collected by the D0 detector at the Fermilab Tevatron ppbar Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section dsigma/dp_T^gamma, where p_T^gamma is the momentum of the photon in the plane transverse to the beamline. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the transverse momentum spectrum of the photon to place limits on anomalous ZZgamma and Zgammagamma couplin…
Measurement of Associated Production ofZBosons with Charm Quark Jets inpp¯Collisions ats=1.96 TeV
2014
We present the first measurements of the ratios of cross sections sigma(p (p) over bar -> Z + c jet)/sigma(p (p) over bar -> Z + jet) and sigma(p (p) over bar -> Z + jet)/sigma(p (p) over bar -> Z + b jet) for the associated production of a Z boson with at least one charm or bottom quark jet. Jets have transverse momentum p(T)(jet) > 20 GeV and pseudorapidity vertical bar eta(jet)vertical bar collisions collected with the D0 detector at the Fermilab Tevatron Collider at root s = 1.96 TeV. The measurements show significant deviations from perturbative QCD calculations and predictions from various event generators.
Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb
2015
et al.
Precision Measurement ofCPViolation inBS0→J/ΨK+K−Decays
2015
The time-dependent CP asymmetry in B-S(0) -> J/Psi K+K- decays is measured using pp collision data, corresponding to an integrated luminosity of 3.0 fb(-1), collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96 000 B-S(0) -> J/Psi K+K- decays, the CP-violating phase phi(s) is measured, as well as the decay widths GL and GH of the light and heavy mass eigenstates of the B-s(0)-(B) over bar (0)(s) system. The values obtained are phi(s) = -0.058 +/- 0.049 +/- 0.006 rad, Gamma(s) equivalent to (Gamma(L) + Gamma(H))/2 = 0.6603 +/- 0.0027 +/- 0.0015 ps(-1), and Delta Gamma(s) equivalent to Gamma(L)-Gamma(H) = 0.0805 +/- 0.0091 +/- 0.0032 ps(-1), where the f…
Measurement of the pp¯→W+b+X production cross section at s=1.96 TeV
2013
We present a measurement of the cross section for $W$ boson production in association with at least one {$b$-quark} jet in proton-antiproton collisions. The measurement is made using data corresponding to an integrated luminosity of 6.1\ifb recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV. We measure an inclusive cross section of {$\sigma(W \sim(\to\mu\nu) + b + X) = 1.04 \pm 0.05\thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb} and $\sigma(W (\to e\nu) + b + X) = 1.00$ \pm 0.04 \thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb in the phase space defined by $p_T^\nu > 25$ GeV, $p_T^{\text{$b$-jet}}>20$ GeV, $|\eta^{\text{$b$-jet}}| 20$ GeV and…
Evidence for Simultaneous Production ofJ/ψandϒMesons
2016
We report evidence for the simultaneous production of $J/\psi$ and $\Upsilon$ mesons in 8.1 fb$^{-1}$ of data collected at $\sqrt{s}=$1.96 TeV by the D0 experiment at the Fermilab $p \bar p$ Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, $\sigma_{eff}=2.2\pm 0.7\mbox{(stat)} \pm 0.9 \mbox{(syst)} ~\mbox{mb}$.
Measurement of the Effective Weak Mixing Angle in pp¯→Z/γ*→ℓ+ℓ− Events
2018
We present a measurement of the effective weak mixing angle parameter sin(2)theta(l)(eff) in p (p) over bar -> Z/gamma* -> mu(+)mu(-) events at a center-of-mass energy of 1.96 TeV, collected by the D0 detector at the Fermilab Tevatron Collider and corresponding to 8.6 fb(-1) of integrated luminosity. The measured value of sin(2)theta(l)(eff)[mu mu] = 0.23016 +/- 0.00064 is further combined with the result from the D0 measurement in p (p) over bar -> Z/gamma* -> e(+)e(-) events, resulting in sin(2)theta(l)(eff)[comb] = 0.23095 +/- 0.00040. This combined result is the most precise measurement from a single experiment at a hadron collider and is the most precise determination using the couplin…
Measurement of the top quark pair production cross section in thelepton+jetschannel in proton-antiproton collisions ats=1.96 TeV
2011
We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we determine simultaneously the $t\bar{t}$ cross section and the ratio of the production rates of $W$+heav…
Determination of the strong coupling constant from the inclusive jet cross section inpp¯collisions ats=1.96 TeV
2009
We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.
Evidence for the Strangeness-Changing Weak DecayΞb−→Λb0π−
2015
Using a pp collision data sample corresponding to an integrated luminosity of 3.0 fb^{-1}, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Ξ_{b}^{-}→Λ_{b}^{0}π^{-}. No b hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be f_{Ξ_{b}^{-}}/f_{Λ_{b}^{0}}B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-})=(5.7±1.8_{-0.9}^{+0.8})×10^{-4},where f_{Ξ_{b}^{-}} and f_{Λ_{b}^{0}} are the b→Ξ_{b}^{-} and b→Λ_{b}^{0} fragmentation fractions, and B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-}) is the branching fraction. Assuming f_{Ξ_{b}^{-}}/f_{Λ_{b}^{0}} is bounded b…
Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production
2013
We present measurements of lepton (l) angular distributions in ttbar -> W+ b W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4fb^-1, collected with the D0 detector at the Fermilab Collider, we find that the angular distributions of l- relative to anti-protons and l+ relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat) +- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted…
Forward-backward asymmetry in top quark-antiquark production
2011
Made available in DSpace on 2022-04-29T02:17:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-12 We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4fb -1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the tt̄ forward-backward asymmetry to be (9.2±3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6±6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark deca…
Combination of CDF and D0 measurements of the W boson helicity in top quark decays
2012
Aaltonen, T. et al.
Precision Measurement of the RatioB(t→Wb)/B(t→Wq)and Extraction ofVtb
2011
We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s or b quark, in the lepton+jets and dilepton ttbar final states. The measurement uses data from 5.4 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the CKM matrix element |Vtb| as |Vtb| = 0.95 +/- 0.02, assuming unitarity of the 3x3 CKM matrix.
Measurement of the forward-backward asymmetry ofΛandΛ¯production inpp¯collisions
2016
We study $\Lambda$ and $\bar{\Lambda}$ production asymmetries in $p \bar{p} \rightarrow \Lambda (\bar{\Lambda}) X$, $p \bar{p} \rightarrow J/\psi \Lambda (\bar{\Lambda}) X$, and $p \bar{p} \rightarrow \mu^\pm \Lambda (\bar{\Lambda}) X$ events recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV. We find an excess of $\Lambda$'s ($\bar{\Lambda}$'s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $\bar{\Lambda}/\Lambda$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of "rapidity loss", i.e., th…
Search for weakly decaying b -flavored pentaquarks
2018
Investigations of the existence of pentaquark states containing a single $b$ (anti)quark decaying weakly into four specific final states J/$\psi K^+\pi^- p$, J/$\psi K^- \pi^- p$, J/$\psi K^- \pi^+ p$, and $J/\psi \phi (1020) p$ are reported. The data sample corresponds to an integrated luminosity of 3.0/fb in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the $\Lambda_b$.
Model-independent confirmation of theZ(4430)−state
2015
The decay $B^0\to \psi(2S) K^+\pi^-$ is analyzed using $\rm 3~fb^{-1}$ of $pp$ collision data collected with the LHCb detector. A model-independent description of the $\psi(2S) \pi$ mass spectrum is obtained, using as input the $K\pi$ mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the $\psi(2S)\pi$ mass spectrum can be described in terms of $K\pi$ reflections alone is rejected with more than 8$\sigma$ significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the $Z(4430)^-$ exotic sta…
Dalitz plot analysis ofB0→D¯0π+π−decays
2015
The resonant substructures of $B^0 \to \overline{D}^0 \pi^+\pi^-$ decays are studied with the Dalitz plot technique. In this study a data sample corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collisions collected by the LHCb detector is used. The branching fraction of the $B^0 \to \overline{D}^0 \pi^+\pi^-$ decay in the region $m(\overline{D}^0\pi^{\pm})>2.1$ GeV$/c^2$ is measured to be $(8.46 \pm 0.14 \pm 0.29 \pm 0.40) \times 10^{-4}$, where the first uncertainty is statistical, the second is systematic and the last arises from the normalisation channel $B^0 \to D^*(2010)^-\pi^+$. The $\pi^+\pi^-$ S-wave components are modelled with the Isobar and K-matrix formalisms. …
Search for Higgs boson production in oppositely charged dilepton and missing energy events inpp¯collisions ats=1.96 TeV
2012
We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in $H\rightarrow WW$ decays. The events are selected from data corresponding to 8.6 \ifb\ of integrated luminosity in $p \bar{p}$ collisions at $\sqrt{s}=1.96$ TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.
Search for first generation leptoquark pair production in the electron + missing energy + jets final state
2011
We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb$^{-1}$ collected with the D0 detector at the Fermilab Tevatron Collider in ppbar collisions at $\sqrt{s}=1.96$ TeV. In the channel $LQ \bar{LQ} \rightarrow e\nu_e qq'$, where q, q' are u or d quarks, no significant excess of data over background is observed, and we set a 95% C.L. lower limit of 326 GeV on the leptoquark mass, assuming equal probabilities of leptoquark decays to eq and $\nu_e q'$.
Differential branching fraction and angular analysis of the decay $B^{0} \to K^{*0} \mu^{+}\mu^{-}$
2013
The angular distribution and differential branching fraction of the decay B-0 -> K*(0)mu(+)mu(-) are studied using a data sample, collected by the LHCb experiment in pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.0 fb(-1). Several angular observables are measured in bins of the dimuon invariant mass squared, q(2). A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q(0)(2) = 4.9 +/- 0.9 GeV2/c(4), where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
Search for the Standard Model Higgs Boson in AssociatedWHProduction in9.7 fb−1ofpp¯Collisions with the D0 Detector
2012
We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a b-quark jet. The search is primarily sensitive to WH→lνbb production and uses data corresponding to 9.7 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp Collider at √s = 1.96 TeV. We observe agreement between the data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2 × σ(SM), where σ(SM) is the standard model Higgs boson production cross section, whi…
Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs.
2015
et al.
Determination of γ and−2βsfrom charmless two-body decays of beauty mesons
2015
Using the latest LHCb measurements of time-dependent CP violation in the B-s(0) -> K+K- decay, a U-spin relation between the decay amplitudes of B-s(0) -> K+K- and B-0 -> p(+)p(-) decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B-s(0) mixing phase -2 beta(s). Results from an extended approach, which uses additional inputs on B-0 -> pi(0)pi(0) and B+ -> pi(+)pi(0) decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value gamma =( 63.5(-6.7)(+7.2))degrees modulo 180 degrees is determined. In an a…
Search for direct CP violation in D0→h−h+ modes using semileptonic B decays
2013
A search for direct CP violation in D0 -> h- h+ (where h=K or pi) is presented using data corresponding to an integrated luminosity of 1.0 fb^-1 collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. The analysis uses D0 mesons produced in inclusive semileptonic b-hadron decays to the D0 mu X final state, where the charge of the accompanying muon is used to tag the flavour of the D0 meson. The difference in the CP-violating asymmetries between the two decay channels is measured to be Delta A_CP = A_CP(K-K+) - A_CP(pi-pi+) = (0.49 +- 0.30 (stat) +- 0.14 (syst)) % . This result does not confirm the evidence for direct CP violation in the charm sector reported in other…
Jet energy scale determination in the D0 experiment
2013
The calibration of jet energy measured in the \DZero detector is presented, based on ppbar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with photon+jet, Z+jet and dijet{} events, with jet transverse momentum pT > 6 GeV and pseudorapidity range |eta| < 3.6. The corrections are measured separately for data and simulation, achieving a precision of 1.4%-1.8% for jets in the central part of the calorimeter and up to 3.5% for the jets with pseudorapidity…
Search for ResonantWWandWZProduction inpp¯Collisions ats=1.96 TeV
2011
We search for resonant WW or WZ production using up to 5.4 fb-1 of integrated luminosity collected by the D0 experiment in Run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass using the sequential standard model (SSM) W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude an SSM W' boson in the mass range 180 - 690 GeV and a Randall-Sundrum graviton in the range 300 - 754 GeV at 95% CL.
Double parton interactions inγ+3jet events inpp¯collisions ats=1.96 TeV
2010
We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single ppbar collision at sqrt{s}=1.96 TeV. The DP fraction and effective cross section (sigma_eff), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2 within the range 15 < pT_jet2 < 30 GeV. In this range, f_DP varies between 0.23 < f_DP < 0.47, while sigma_eff has the average value sigma_eff_ave = 16.4 +- 0.3(stat) +- 2.3(syst) mb.
Search for Higgs bosons of the minimal supersymmetric standard model in pp¯ collisions at s=1.96 TeV
2012
We report results from searches for neutral Higgs bosons produced in p-pbar collisions recorded by the Dzero experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tautau final state and in association with a b quark in the btautau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tanBeta>20-30 for Higgs boson ma…
Study of double parton interactions indiphoton+dijetevents inpp¯collisions ats=1.96 TeV
2016
We use a sample of diphoton+dijet events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be σeff=19.3±1.4(stat)±7.8(syst) mb. The sample was collected by the D0 detector at the Fermilab Tevatron collider in $$p\bar{p}$$ collisions at $$\sqrt{s} = 1.96$$ TeV and corresponds to an integrated luminosity of 8.7 fb-1.
Measurement of theWBoson Production Charge Asymmetry inpp¯→W+X→eν+XEvents ats=1.96 TeV
2014
We present a measurement of the W boson production charge asymmetry in p (p) over bar -> W + X -> ev + X events at a center of mass energy of 1.96 TeV, using 9.7 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum is determined by using a neutrino weighting method, and the asymmetry is measured as a function of the W boson rapidity. The measurement extends over wider electron pseudorapidity region than previous results and is the most precise to date, allowing for precise determination of proton parton distribution functions in global fits.
Search for scalar bottom quarks and third-generation leptoquarks in pp¯ collisions at s=1.96 TeV
2010
We report the results of a search for pair production of scalar bottom quarks ((b) over bar (1)) and scalar third-generation leptoquarks (LQ(3)) in 5.2 fb(-1) of p (p) over bar collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino ((chi) over bar (1)(0)) and a b quark, and we set 95% C.L. lower limits on their production in the (m((b) over bar1), m((chi) over bar 10)) mass plane such as m((b) over bar1) > 247 GeV for m( 10) = 0 and m((chi) over bar 10) > 110 GeV for 160 m(<(b) over bar1) < 200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the ma…
Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
2012
We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different tran…
Search for a Resonance Decaying intoWZBoson Pairs inpp¯Collisions
2010
We present the first search for an electrically charged resonance W' decaying to a WZ boson pair using 4.1 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. The WZ pairs are reconstructed through their decays into three charged leptons (l = e, mu). A total of 9 data events is observed in good agreement with the background prediction. We set 95% C.L. limits on the W'WZ coupling and on the W' production cross section multiplied by the branching fractions. We also exclude W' masses between 188 and 520 GeV within a simple extension of the standard model and set the most restrictive limits to date on low-scale technicolor models.
Measurements of the Λb0→J/ψΛ decay amplitudes and the Λb0 polarisation in pp collisions at s=7 TeV
2013
An angular analysis of Λ0b→J/ψΛ decays is performed using a data sample corresponding to 1.0 fb−1 collected in pp collisions at √s=7 TeV with the LHCb detector at the LHC. A parity violating asymmetry parameter characterising the Λ0b→J/ψΛ decay of 0.05±0.17±0.07 and a Λ0b transverse production polarisation of 0.06±0.07±0.02 are measured, where the first uncertainty is statistical and the second systematic.
Measurement of the anomalous like-sign dimuon charge asymmetry with9 fb−1ofpp¯collisions
2011
We present an updated measurement of the anomalous like-sign dimuon charge asymmetry A(sl)(b) for semileptonic b-hadron decays in 9.0 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy of root s = 1.96 TeV at the Fermilab Tevatron collider. We obtain A(sl)(b) = (-0.787 +/- 0.172(stat) +/- 0.093(syst)%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semileptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semileptonic b-hadron decays.
Search for the Standard Model Higgs Boson inZH→ℓ+ℓ−bb¯Production with the D0 Detector in9.7 fb−1ofpp¯Collisions ats=1.96 TeV
2012
We acknowledge support from the DOE and NSF (USA); CEA and CNRS/IN2P3 (France); FASI, Rosatom, and RFBR (Russia); CNPq, FAPERJ, FAPESP, and FUNDUNESP (Brazil); DAE and DST (India); Colciencias (Colombia); CONACyT (Mexico); KRF and KOSEF (Korea); CONICET and UBACyT (Argentina); FOM (Netherlands); STFC and the Royal Society (United Kingdom); MSMT and GACR (Czech Republic); CRC Program and NSERC (Canada); BMBF and DFG (Germany); SFI (Ireland); The Swedish Research Council (Sweden); and CAS and CNSF (China).
Measurement of theWZ→ℓνℓℓcross section and limits on anomalous triple gauge couplings inpp¯collisions ats=1.96TeV
2011
We present a new measurement of the WZ -> lvll (l = e, mu) cross section and limits on anomalous triple gauge couplings. Using 4.1 fb(-1) of integrated luminosity of p (p) over bar collisions at root s = 1.96 TeV, we observe 34 WZ candidate events with an estimated background of 6.0 +/- 0.4 events. We measure the WZ production cross section to be 3.89(-0.90)(+1.07) pb, in good agreement with the standard model prediction. We find no evidence for anomalous WWZ couplings and set 95% C.L. limits on the coupling parameters, -0.077 < lambda(z) < 0.093 and -0.029 < Delta kappa(z) < 0.080 in the HISZ parameterization for a Lambda = 2 TeV form factor scale. These are the best limits to date obtaine…
Search for pair production of the scalar top quark in muon+tau final states
2012
We present a search for the pair production of scalar top quarks ($\tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tilde{\nu}$). We investigate final states arising from $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\mu\tau \tilde{\nu} \tilde{\nu}$ and $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\tau\tau \tilde{\nu} \tilde{\nu}$. With no si…
Search for a Higgs boson in diphoton final states with the D0 detector in9.6 fb−1ofpp¯collisions ats=1.96 TeV
2013
We present a search for a Higgs boson decaying into a pair of photons based on 9.6 fb-1 of p-pbar collisions at sqrt(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The search employs multivariate techniques to discriminate signal from the non-resonant background and is separately optimized for a standard model and a fermiophobic Higgs boson. No significant excess of data above the background prediction is observed and upper limits on the product of the cross section and branching fraction are derived at the 95% confidence level as a function of Higgs boson mass. For a standard model Higgs boson with mass of 125 GeV, the observed (expected) upper limits are a f…
Muon reconstruction and identification with the Run II D0 detector
2013
We present an overview of the muon reconstruction and identification methods employed by the D0 Collaboration to analyze the Run II (2001-2011) ppbar data of the Fermilab Tevatron collider at sqrt s = 1.96 TeV. We discuss the performance of these methods, how it is measured using D0 data, and how it is properly modeled by the D0 simulation program. In its pseudorapidity acceptance, eta< 2, the muon system identifies high-pT muons (pT>10 GeV) with efficiencies ranging from 72% to 89%. Muons tracks are reconstructed in the D0 central tracking system with efficiencies ranging from 85% to 92% and with a typical relative momentum resolution of 10% for pT = 40 GeV. Isolation criteria reject…
Search for new fermions ("quirks") at the Fermilab Tevatron Collider
2010
We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in $2.4$ fb$^{-1}$ of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron $p\bar{p}$ collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like {\it SU(N)} sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107 ~GeV for the mass of a charged quirk with strong dynamics scale $\Lambda$ in the range from 10 keV to 1 MeV.
Search forZH→ℓ+ℓ−bb¯production in9.7 fb−1ofpp¯collisions with the D0 detector
2013
We present a search for the standard model (SM) Higgs boson produced in association with a Z boson in 9.7 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider at sqrt{s} = 1.96 TeV. Selected events contain one reconstructed Z -> e+e- or Z -> mu+mu- candidate and at least two jets, including at least one jet likely to contain a b quark. To validate the search procedure, we also measure the cross section for ZZ production, and find that it is consistent with the SM expectation. We set upper limits at the 95% C.L. on the product of the ZH production cross section and branching ratio B(H -> bbbar) for Higgs boson masses 90
Measurement of the forward-backward asymmetries in the production ofΞandΩbaryons inpp¯collisions
2016
We measure the forward-backward asymmetries $A_{\rm FB}$ of charged $\Xi$ and $\Omega$ baryons produced in $p \bar{p}$ collisions recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s} = 1.96$ TeV as a function of the baryon rapidity $y$. We find that the asymmetries $A_{\rm FB}$ for charged $\Xi$ and $\Omega$ baryons are consistent with zero within statistical uncertainties.
Search for the standard model Higgs boson in tau lepton final states
2012
We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb^{-1} collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to tau lepton pairs or W boson pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 1…
Measurement of the forward-backward asymmetry in top quark-antiquark production inpp¯collisions using thelepton+jetschannel
2014
We present a measurement of the forward-backward asymmetry in top quark-antiquark production using the full Tevatron Run II data set collected by the D0 experiment at Fermilab. The measurement is performed in lepton + jets final states using a new kinematic fitting algorithm for events with four or more jets and a new partial reconstruction algorithm for events with only three jets. Corrected for detector acceptance and resolution effects, the asymmetry is evaluated to be A(FB) = (10.6 +/- 3.0)%. Results are consistent with the standard model predictions which range from 5.0% to 8.8%. We also present the dependence of the asymmetry on the invariant mass of the top quark-antiquark system and…
Measurement of trilinear gauge boson couplings fromWW+WZ→lνjjevents inpp¯collisions ats=1.96 TeV
2009
We present a direct measurement of trilinear gauge boson couplings at gamma WW and ZWW vertices inWW and WZ events produced in p (p) over bar collisions at root s = 1:96 TeV. We consider events with one electron or muon, missing transverse energy, and at least two jets. The data were collected using the D0 detector and correspond to 1:1 fb(-1) of integrated luminosity. Considering two different relations between the couplings at the gamma WW and ZWW vertices, we measure these couplings at 68% C.L. to be kappa(gamma) = 1.07(-0.29)(+0.26) lambda = 0.00(-0.06)(+0.00), and g(1)(Z) = 1.04(-0.09)(+0.09) in a scenario respecting SU(2)(L) circle times U(1)(Y) gauge symmetry and kappa = 1.04(-0.11)(…
Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wγ production in pp¯ collisions at s=1.96 TeV
2012
We present searches for the anomalous γWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wγ, WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6fb -1 of integrated luminosity collected by the D0 detector in pp- collisions at s=1.96TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters δκ γ, λ, and δg1Z for a cutoff energy scale Λ=2TeV. The combined 68% C.L. limits are -0.057lδκ γl0.154, -0.015lλl0.028, and -0.008lδg1Zl0.054 for the LEP parameterization, and -0.007lδκl0.081 an…
Search for anomalous Wtb couplings in single top quark production in pp¯ collisions at s=1.96 TeV
2012
We present new direct constraints on a general $Wtb$ interaction using data corresponding to an integrated luminosity of 5.4 fb$^{-1}$ collected by the D0 detector at the Tevatron $p\bar{p}$ collider. The standard model provides a purely left-handed vector coupling at the $Wtb$ vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the $Wtb$ coupling.
Measurement of the Forward-Backward Asymmetry in the Production ofB±Mesons inpp¯Collisions ats=1.96 TeV
2015
We present a measurement of the forward-backward asymmetry in the production of B-+/- mesons, A(FB)(B-+/-) using B-+/- -> J/ Psi K-+/- decays in 10.4 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment during Run II of the Tevatron collider. A nonzero asymmetry would indicate a preference for a particular flavor, i.e., b quark or (b) over bar antiquark, to be produced in the direction of the proton beam. We extract A(FB) (B-+/-) from a maximum likelihood fit to the difference between the numbers of forward-and backward-produced B-+/- mesons. We measure an asymmetry consistent with zero: A(FB) (B-+/-) = [-0.24 +/- 0.41 (stat) +/- 0.19 (syst)] %.
Quantum numbers of theX(3872)state and orbital angular momentum in itsρ0J/ψdecay
2015
Angular correlations in B+→X(3872)K+ decays, with X(3872)→ρ0J/ψ, ρ0→π+π− and J/ψ→μ+μ−, are used to measure orbital angular momentum contributions and to determine the JPC value of the X(3872) meson. The data correspond to an integrated luminosity of 3.0 fb−1 of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be JPC=1++. The X(3872) is found to decay predominantly through S wave and an upper limit of 4% at 95% C.L. is set on the fraction of D wave.
Bs0lifetime measurement in theCP-odd decay channelBs0→J/ψ f0(980)
2016
The lifetime of the $B^{0}_{s}$ meson is measured in the decay channel $B^{0}_{s} \to J/\psi\mbox{ }\pi^+ \pi^-$ with $880 \leq M_{\pi^+\pi^-} \leq 1080$ MeV/$c^2$, which is mainly a CP-odd state and dominated by the $f_{0}(980)$ resonance. In 10.4 fb$^{-1}$ of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the $B^{0}_{s}$ meson is measured to be $\tau(B^{0}_{s}) = 1.70\pm 0.14 \mbox{ (stat)} \pm 0.05 \mbox{ (syst) ps}$. Neglecting CP violation in $B_s^0/\bar{B}_s^0$ mixing, the measurement can be translated into the width of the heavy mass eigenstate of the $B^0_s$, $\Gamma_H = 0.59 \pm 0.05 \mbox{ (stat)} \pm 0.02 \mbox{ (syst)} \mbox{ ps$^{-1}$}$.
Search for the standard model Higgs boson inℓν+jetsfinal states in9.7 fb−1ofpp¯collisions with the D0 detector
2013
Searches for the Higgs boson have started as soon as the underlying model for particle mass generation has been proposed, and the search went on for several decades at LEP, Tevatron and LHC. Last year the ATLAS and CMS Collaborations at the Large Hadron Collider (LHC) have reported the observation of a new boson [1, 2]. At the same time the CDF and D0 Collaborations reported combined evidence for a particle, with a mass consistent with that of the new boson observed at LHC [3]. This thesis presents the search by the D0 collaboration for the SM Higgs boson using events containing one isolated charged lepton (l = e or μ), a significant imbalance in transverse energy (6ET ), and two or more je…
Measurement of the normalized Z/γ∗→μ+μ− transverse momentum distribution in pp¯ collisions at s=1.96 TeV
2010
We present a new measurement of the Z/gamma* transverse momentum distribution in the range 0-330 GeV, in proton-antiproton collisions at root s = 1.96 TeV. The measurement uses 0.97 fb(-1) of integrated luminosity recorded by the D0 experiment and is the first using the Z/gamma* -> mu(+)mu(-) + X channel at this center-of-mass energy. This is also the first measurement of the Z/gamma* transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/gamma* in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation …
Precise measurement of the top quark mass in the dilepton channel at D0
2011
We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.
Model independent search for new phenomena inpp¯collisions ats=1.96 TeV
2012
We describe a model independent search for physics beyond the standard model in lepton final states. We examine 117 final states using 1.1 fb$^{-1}$ of $p \bar{p}$ collisions data at $\sqrt{s} = 1.96$ TeV collected with the D0 detector. We conclude that all observed discrepancies between data and model can be attributed to uncertainties in the standard model background modeling, and hence we do not see any evidence for physics beyond the standard model.
Odderon Exchange from Elastic Scattering Differences between pp and pp¯ Data at 1.96 TeV and from pp Forward Scattering Measurements
2021
We describe an analysis comparing the p p ¯ elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in p p collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV using a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of s = 1.96 TeV , are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the p p cross section. The two data sets disagree at the 3.4 σ level and thus provide evidence for the t -channel exchange of a colorless, C -odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of th…
Search for violation of Lorentz invariance in top quark pair production and decay
2012
Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5.3 fb$^{-1}$ of integrated luminosity, we search for violation of Lorentz invariance by examining the \ttbar production cross section in lepton+jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the \ttbar production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices $(c_Q)_{\mu\nu 33}$ and $(c_U)_{\mu\nu 33}$ containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Wit…
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
2016
We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV.
Observation of Photon Polarization in theb→sγTransition
2014
This Letter presents a study of the flavor-changing neutral current radiative $B^{\pm} \to K^{\pm}\pi^{\mp}\pi^{\pm}\gamma$ decays performed using data collected in proton-proton collisions with the LHCb detector at $7$ and $8\,$TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of $3\,\text{fb}^{-1}$, nearly $14\,000$ signal events are reconstructed and selected, containing all possible intermediate resonances with a $K^{\pm}\pi^{\mp}\pi^{\pm}$ final state in the $[1.1, 1.9]\,$GeV/$c^{2}$ mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in interva…
Measurements ofCPviolation in the three-body phase space of charmlessB±decays
2014
The charmless three-body decay modes B±→K±π+π−, B±→K±K+K−, B±→π±K+K− and B±→π±π+π− are reconstructed using data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb detector. The inclusive CP asymmetries of these modes are measured to be ACP(B±→K±π+π−)=+0.025±0.004±0.004±0.007,ACP(B±→K±K+K−)=−0.036±0.004±0.002±0.007,ACP(B±→π±π+π−)=+0.058±0.008±0.009±0.007,ACP(B±→π±K+K−)=−0.123±0.017±0.012±0.007, where the first uncertainty is statistical, the second systematic, and the third is due to the CP asymmetry of the B±→J/ψK± reference mode. The distributions of these asymmetries are also studied as functions of position in the Dalitz plot and suggest contributions from res…
Measurement of the differential cross sections for isolated direct photon pair production in pp¯ collisions at s=1.96 TeV
2013
We present measurements of direct photon pair production cross sections using 8.5 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. The results are presented as differential distributions of the photon pair invariant mass d sigma/dM(gamma gamma), pair transverse momentum d sigma/dp(T)(gamma gamma) azimuthal angle between the photons d sigma/d Delta(phi)(gamma gamma), and polar scattering angle in the Collins-Soper frame d sigma/d vertical bar cos theta*vertical bar. Measurements are performed for isolated photons with transverse momenta p(T)(gamma) > 18 (17) GeV for the leading (next-to-leading) photon in P-T, pseudorapidities vertical bar eta(g…
Search for Higgs Boson Production in Dilepton and Missing Energy Final States with5.4 fb−1ofpp¯Collisions ats=1.96 TeV
2010
A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb-1 of integrated luminosity in p-pbar collisions at sqrt(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at Higgs boson mass of 165 GeV.
Searches for violation of lepton flavour and baryon number in tau lepton decays at LHCb
2013
Searches for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-) and the lepton flavour and baryon number violating decays tau(-) -> (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) have been carried out using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb(-1), taken by the LHCb experiment at root s = 7 TeV. No evidence has been found for any signal, and limits have been set at 90% confidence level on the branching fractions: B(tau(-) -> mu(-)mu(+)mu(-) mu(+)mu(-)) p mu(-)mu(-)) (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) decay modes represent the first direct experimental limits on these channels.
Measurement of the c0 Baryon Lifetime
2018
We report a measurement of the lifetime of the $��_c^0$ baryon using proton-proton collision data at center-of-mass energies of 7 and 8~TeV, corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb experiment. The sample consists of about 1000 $��_b^-\to��_c^0��^-\bar��_�� X$ signal decays, where the $��_c^0$ baryon is detected in the $pK^-K^-��^+$ final state and $X$ represents possible additional undetected particles in the decay. The $��_c^0$ lifetime is measured to be $��_{��_c^0} = 268\pm24\pm10\pm2$ fs, where the uncertainties are statistical, systematic, and from the uncertainty in the $D^+$ lifetime, respectively. This value is nearly four times larger than, …
Search for Violation ofCPTand Lorentz Invariance inBs0Meson Oscillations
2015
We present the first search for CPT-violating effects in the mixing of B-s(0) mesons using the full Run II data set with an integrated luminosity of 10.4 fb(-1) of proton-antiproton collisions coll ...
Study ofCPviolation inB∓→Dh∓(h=K,π) with the modesD→K∓π±π0,D→π+π−π0andD→K+K−π0
2015
An analysis of the decays of B--/+ -> DK -/+ and B--/+ -> D pi(-/+) is presented in which the D meson is reconstructed in the three-body final states K--/+pi(+/-)pi(0), pi(+)pi(-)pi(0) and K+K-pi(0). Using data from LHCb corresponding to an integrated luminosity of 3.0 fb(-1) of pp collisions, measurements of several CP observables are performed. First observations are obtained of the suppressed Atwood-Dunietz-Soni decay B--/+ -> [pi K-+(+/-)pi(0)](D)pi(-/+) and the quasi-Gronau-London-Wyler decay B--/+ -> [K+K-pi(0)](D)pi(-/+). The results are interpreted in the context of the unitarity triangle angle gamma and related parameters.
Model-independent measurement of t-channel single top quark production in pp¯ collisions at s=1.96 TeV
2011
We present a model-independent measurement of $t$-channel electroweak production of single top quarks in $\ppbar$ collisions at $\sqrt{s}=1.96\;\rm TeV$. Using $5.4\;\rm fb^{-1}$ of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of $b$ quarks, we measure a cross section $\sigma({\ppbar}{\rargap}tqb+X) = 2.90 \pm 0.59\;\rm (stat+syst)\; pb$ for a top quark mass of $172.5\;\rm GeV$. The probability of the background to fluctuate and produce a signal as large as the one observed is $1.6\times10^{-8}$, corresponding…
Search for charged massive long-lived particles
2012
We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss $(dE/dx)$ inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.
Precision Measurement of the Mass and Lifetime of the Ξ[0 over b] Baryon
2014
Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 $\Xi_b^0\to\Xi_c^+\pi^-$, $\Xi_c^+\to pK^-\pi^+$ signal decays are reconstructed. From this sample, the first measurement of the $\Xi_b^0$ baryon lifetime is made, relative to that of the $\Lambda_b^0$ baryon. The mass differences $M(\Xi_b^0)-M(\Lambda_b^0)$ and $M(\Xi_c^+)-M(\Lambda_c^+)$ are also measured with precision more than four times better than the current world averages. The resulting values are $\frac{\tau_{\Xi_b^0}}{\tau_{\Lambda_b^0}} = 1.006\pm0.018\pm0.010$, $M(\Xi_b^0) - M(\Lambda_b^0) = 172.44\pm0.39\pm…
First measurement of the charge asymmetry in beauty-quark pair production.
2014
The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in b[bar over b] pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb[superscript −1] collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the b[bar over b] system. The results obtained are A[b[bar over b] over C](40 105 GeV/c[superscript 2]) = 1.6 ± 1.7 ± 0.6%, where A[b[bar over b] over C] is defined as the asymmetry in the difference in rapidity between jets formed from the beauty q…
Tevatron Run II combination of the effective leptonic electroweak mixing angle
2018
The Ministry of Science and Innovation and the Consolider-Ingenio 2010 Program and the European Union community Marie Curie Fellowship Contract No. 302103.
Determination of the pole and MS¯ masses of the top quark from the tt¯ cross section
2011
We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the ttbar cross section measured in the lepton+jets channel in ppbar collisions at sqrt(s)=1.96 TeV using 5.3 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and MSbar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
Search for a narrowtt¯resonance inpp¯collisions ats=1.96 TeV
2012
We report a search for a narrow ttbar resonance that decays into a lepton+jets final state based on an integrated luminosity of 5.3/fb of proton-antiproton collisions at sqrt{s}=1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the production cross section of such a resonance multiplied by its branching fraction to ttbar which we compare to predictions for a leptophobic topcolor Z' boson. We exclude such a resonance at the 95% confidence level for masses below 835 GeV.
Combined search for the Higgs boson with the D0 experiment
2013
We perform a combination of searches for standard model Higgs boson production in $p\bar{p}$ collisions recorded by the D0 detector at the Fermilab Tevatron Collider at a center of mass energy of $\sqrt{s}=1.96$ TeV. The different production and decay channels have been analyzed separately, with integrated luminosities of up to 9.7 fb$^{-1}$ and for Higgs boson masses $90\leq M_H \leq 200$ GeV. We combine these final states to achieve optimal sensitivity to the production of the Higgs boson. We also interpret the combination in terms of models with a fourth generation of fermions, and models with suppressed Higgs boson couplings to fermions. The result excludes a standard model Higgs boson …
Observation of a narrow mass state decaying intoΥ(1S)+γinpp¯collisions ats=1.96 TeV
2012
Using data corresponding to an integrated luminosity of 1.3 fb(-1), we observe a narrow mass state decaying into Gamma(1S) + gamma, where the Gamma(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 +/- 0.014(stat) +/- 0.017(syst) GeV/c(2), which is consistent with that of the state recently observed by the ATLAS Collaboration.
Measurement of spin correlation between top and antitop quarks produced in pp¯ collisions at s=1.96 TeV
2016
Department of Energy (United States of America); National Science Foundation (United States of America); Alternative Energies and Atomic Energy Commission (France); National Center for Scientific Research/ National Institute of Nuclear and Particle Physics (France); Ministry of Education and Science of the Russian Federation (Russia); National Research Center "Kurchatov Institute" of the Russian Federation (Russia); Russian Foundation for Basic Research (Russia); National Council for the Development of Science and Technology (Brazil); Carlos Chagas Filho Foundation for the Support of Research in the State of Rio de Janeiro (Brazil); Department of Atomic Energy (India); Department of Science…
Measurement of the production fraction times branching fractionf(b→Λb)·B(Λb→J/ψΛ)
2011
The \Lambda_b(udb) baryon is observed in the decay \Lambda_b --> J/\psi \Lambda using 6.1 fb^{-1} of p\bar{p} collisions collected with the D0 detector at \sqrt{s}=1.96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B^0 --> J/\psi K^0_s is measured to be 0.345 \pm 0.034 (stat.) \pm 0.033 (syst.) \pm 0.003 (PDG). Using the world average value of f(b --> B^0)B(B^0 --> J/\psi K^0_s) = (1.74 \pm 0.08) \times 10^{-5}, we obtain f(b --> \Lambda_b)B(\Lambda_{b} --> J/\psi \Lambda) = (6.01 \pm 0.60 (stat.) \pm 0.58 (syst.) \pm 0.28 (PDG)) \times 10^{-5}. This measurement represents an improvement in precision by about a factor of thre…
Precise Study of theZ/γ*Boson Transverse Momentum Distribution inpp¯Collisions Using a Novel Technique
2011
Using 7.3 pb-1 of ppbar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable \phistar, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the \phistar distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
Evidence for s-channel single top quark production in pp¯ collisions at s=1.96 TeV
2013
We present measurements of the cross sections for the two main production modes of single top quarks in p (p) over bar collisions at root s = 1.96 TeV in the Run II data collected with the DO detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb(-1). The s-channel cross section is measured to be sigma(p (p) over bar -> tb + X) = 1.10(-0.31)(+0.33) pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be sigma(p (p) over bar -> tqb + X) = 3.07(-0.49)(+0.54) pb. We also measure the s + t combined cross section as sigma(p (p) over bar -> tb + X, tqb + X) = 4.11(-0.55)(+0.60) ph and set…
Measurement of CP asymmetries in the decays B0 → K*0 μ+μ- and B+ → K+ μ+μ-
2014
The direct CP asymmetries of the decays B 0 → K *0 μ + μ − and B + → K + μ + μ − are measured using pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected with the LHCb detector. The respective control modes B 0 → J/ψK *0 and B + → J/ψK + are used to account for detection and production asymmetries. The measurements are made in several intervals of μ + μ − invariant mass squared, with the ϕ(1020) and charmonium resonance regions excluded. Under the hypothesis of zero CP asymmetry in the control modes, the average values of the asymmetries are ACP(B0→K∗0μ+μ−)=−0.035±0.024±0.003,ACP(B+→K+μ+μ−)=0.012±0.017±0.001, where the first uncertainties are statistical and the …
Search for Single Vectorlike Quarks inpp¯Collisions ats=1.96 TeV
2011
We present a search for hypothetical vector-like quarks in ppbar collisions at sqrt(s) = 1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb^(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vector-like quarks decaying to W+jet and Z+jet. These are the most stringent mass limits for electroweak single vector-like quark production at hadron colliders.
A novel method for modeling the recoil in W boson events at hadron collider
2009
We present a new method for modeling the hadronic recoil in W->lnu events produced at hadron colliders. The recoil is chosen from a library of recoils in Z->ll data events and overlaid on a simulated W->lnu event. Implementation of this method requires that the data recoil library describe the properties of the measured recoil as a function of the true, rather than the measured, transverse momentum of the boson. We address this issue using a multidimensional Bayesian unfolding technique. We estimate the statistical and systematic uncertainties from this method for the W boson mass and width measurements assuming 1 fb-1 of data from the Fermilab Tevatron. The uncertainties are found…
Measurement of direct photon pair production cross sections in pp¯ collisions at s=1.96 TeV
2010
We present a measurement of direct photon pair production cross sections using 4.2 fb(-1) of data collected with the DO detector at the Fermilab Tevatron p (p) over bar Collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons. In addition, we measure double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators. (C) 2010 Elsevier B.V. All rights reserved.
Search for the Higgs boson in lepton, tau and jets final states
2013
We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with two or more jets using 9.7 fb^{-1} of Run II Fermilab Tevatron Collider data collected with the D0 detector. The analysis is sensitive to Higgs boson production via gluon fusion, associated vector boson production, and vector boson fusion, followed by the Higgs boson decay to tau lepton pairs or to W boson pairs. The ratios of 95% C.L. upper limits on the cross section times branching ratio to those predicted by the standard model are obtained for orthogonal subsamples that are enriched in either H -> tau tau decays or H -> WW decay…
Measurement of the tt¯ production cross section using dilepton events in pp¯ collisions
2011
We present a measurement of the a production cross section sigma((u) over bar) in p (p) over bar collisions at root s = 1.96 TeV using 5.4 fb(-1) of integrated luminosity collected with the D0 detector. We consider final states with at least two jets and two leptons (ee, e mu, mu mu), and events with one jet for the e mu final state as well. The measured cross section is sigma((u) over bar) = 7.36(-0.79)(+0.90)(stat + syst) pb. This result combined with the cross section measurement in the lepton + jets final state yields sigma((u) over bar) = 7.56(-0.56)(+0.63)(stat + syst) pb, which agrees with the standard model expectation. The relative precision of 8% of this measurement is comparable …
Constraints on the unitarity triangle angleγfrom Dalitz plot analysis ofB0→DK+π−decays
2016
The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of B0→DK+π- decays, with D→K+π-, K+K-, and π+π-. The analysis is based on a data sample corresponding to 3.0 fb-1 of pp collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle γ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the B0→DK∗(892)0 decay are determined for the first time. These measurements can be used to improve the sensitivity to γ of existing and future studies of the B0→DK∗(892)0 decay.
Determination of the width of the top quark
2011
We extract the total width of the top quark, Gamma_t, from the partial decay width Gamma(t -> W b) measured using the t-channel cross section for single top quark production and from the branching fraction B(t -> W b) measured in ttbar events using up to 2.3 fb^-1 of integrated luminosity collected by the D0 Collaboration at the Tevatron ppbar Collider. The result is Gamma_t = 1.99 +0.69 -0.55 GeV, which translates to a top-quark lifetime of tau_t = (3.3 +1.3 -0.9) x 10^-25 s. Assuming a high mass fourth generation b' quark and unitarity of the four-generation quark-mixing matrix, we set the first upper limit on |Vtb'| < 0.63 at 95% C.L.
Search for WH associated production in 5.3 fb−1 of pp¯ collisions at the Fermilab Tevatron
2011
We present a search for associated production of Higgs and W bosons in collisions at a center of mass energy of in 5.3 fb−1 of integrated luminosity recorded by the D0 experiment. Multivariate an ...
Search for charged Higgs bosons in top quark decays
2009
We present a search for charged Higgs bosons in top quark decays. We analyze the \eplus, \muplus, $ee$, $e\mu$, $\mu\mu$, \etau and \mutau final states from top quark pair production events, using data from about 1${\text{fb}}^{-1}$ of integrated luminosity recorded by the \dzero experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a $\tau$ lepton and a $\tau$ neutrino and a third one where both decays appear. We extract limits on the branching ratio $B(t\to H^+ b)$ for all these models. We use two method…
Study of the X±(5568) state with semileptonic decays of the Bs0 meson
2018
We present a study of the X±(5568) using semileptonic decays of the Bs0 meson using the full run II integrated luminosity of 10.4 fb-1 in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, X±(5568), in the decay sequence X±(5568)→Bs0π± where Bs0→μ∓Ds±X, Ds±→ϕπ± which is consistent with the previous measurement by the D0 Collaboration in the hadronic decay mode, X±(5568)→Bs0π± where Bs0→J/ψϕ. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding m=5566.9-3.1+3.2(stat)-1.2+0.6(syst) MeV/c2, Γ=18.6-6.1+7.9(s…
Search for anomalous quarticWWγγcouplings in dielectron and missing energy final states inpp¯collisions ats=1.96 TeV
2013
We present a search for anomalous components of the quartic gauge boson coupling WW gamma gamma in events with an electron, a positron and missing transverse energy. The analyzed data correspond to 9.7 fb(-1) of integrated luminosity collected by the D0 detector in p (p) over bar collisions at root s 1.96 TeV. The presence of anomalous quartic gauge couplings would manifest itself as an excess of boosted WW events. No such excess is found in the data, and we set the most stringent limits to date on the anomalous coupling parameters a(0)(W) and a(C)(W). When a form factor with Lambda(cutoff) = 0.5 TeV is used, the observed upper limits at 95% C. L. are vertical bar a(0)(W)/Lambda(2)vertical …
Measurement of the ttbar cross section using high-multiplicity jet events
2010
We present a measurement of the ttbar cross section using high-multiplicity jet events produced in ppbar collisions at sqrt{s}=1.96 TeV. These data were recorded at the Fermilab Tevatron collider with the D0 detector. Events with at least six jets, two of them identified as b jets, were selected from a 1 fb-1 data set. The measured cross section, assuming a top quark mass of 175 GeV/c^2, is 6.9 \pm 2.0 pb, in agreement with theoretical expectations.
Double parton interactions inγ+3jet andγ+b/cjet+2jet events inpp¯collisions ats=1.96 TeV
2014
We determine the fraction of events with double parton (DP) Scattering in a single p (p) over bar collisions at root s = 1.96 TeV in gamma + 3 jet and gamma + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb(-1). The DP fractions and effective cross sections (sigma(eff)) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the gamma + 3 jet and gamma + b/cjet + 2 jet samples of sigma(incl)(eff) = 12.7 +/- 0.2(stat) +/- 1.3(syst) mb and sigma(HF)(eff) = 14.6 +/- 0.6(stat) +/- 3.2(syst) mb, respectively.
Determination of the $X(3872)$ meson quantum numbers
2013
The quantum numbers of the X(3872) meson are determined to be J(PC) = 1(++) based on angular correlations in B+ -> X(3872)K+ decays, where X(3872) -> pi(+) pi(-) j/psi and J/psi -> pi(+) mu(-). The data correspond to 1.0 fb(-1) of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements J(PC) = 2(-+) is rejected with a confidence level equivalent to more than 8 Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
Measurement of top quark polarization in tt¯ lepton+jets final states
2017
Department of Energy (USA); National Science Foundation (USA); Alternative Energies and Atomic Energy Commission and National Center for Scientific Research/National Institute of Nuclear and Particle Physics (France); Ministry of Education and Science of the Russian Federation (Russia); National Research Center "Kurchatov Institute" of the Russian Federation (Russia); Russian Foundation for Basic Research (Russia); Carlos Chagas Filho Foundation for the Support of Research in the State of Rio de Janeiro (Brazil); Department of Science and Technology (India); Administrative Department of Science, Technology and Innovation (Colombia); National Council of Science and Technology (Mexico); Natio…
Search for Diphoton Events with Large Missing Transverse Energy in6.3 fb−1ofpp¯Collisions ats=1.96 TeV
2010
We report a search for diphoton events with large missing transverse energy produced in p (p) over bar collisions at root s = 1.96 TeV. The data were collected with the D0 detector at the Fermilab ...
Measurement of the forward-backward asymmetry inΛb0andΛ¯b0baryon production inpp¯collisions ats=1.96TeV
2015
We measure the forward-backward asymmetry in the production of Lambda(0)(b) and (Lambda) over bar (0)(b) baryons as a function of rapidity in p (p) over bar collisions at root s = 1.96 TeV using 10.4 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. The asymmetry is determined by the preference of Lambda(0)(b) or (Lambda) over bar (0)(b) particles to be produced in the direction of the beam protons or antiprotons, respectively. The measured asymmetry integrated over rapidity y in the range 0.1 < vertical bar y vertical bar < 2.0 is A = 0.04 +/- 0.07(stat) +/- 0.02(syst).
Observation of the Resonant Character of theZ(4430)−State
2014
Resonant structures in B-0 -> psi'pi K--(+) decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 3 fb(-1) collected with the LHCb detector. The data cannot be described with K+pi(-) resonances alone, which is confirmed with a model-independent approach. A highly significant Z(4430)(-) -> psi'pi(-) component is required, thus confirming the existence of this state. The observed evolution of the Z(4430)(-) amplitude with the psi'pi(-) mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin parity is determined unambiguously to be 1(+).
Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states fromtt¯production at the Tevatron
2015
We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in t (t) over bar production in dilepton final states using 9.7 fb(-1) of proton-antiproton collisions at root s = 1.96 TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible t (t) over bar kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of A(t (t) over bar) = (15.0 +/- 6.4(stat) +/- 4.9(syst)) % and a top-quark polarization times spin analyzing power in the beam basis of kappa P…
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
2018
The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of √s=1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is At¯tFB=0.128±0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions.
Search for CP violation using T-odd correlations in D-0 -> K+K-pi(+)pi(-) decays
2014
A search for $CP$ violation using $T$-odd correlations is performed using the four-body $D^0 \to K^+K^-\pi^+\pi^-$ decay, selected from semileptonic $B$ decays. The data sample corresponds to integrated luminosities of $1.0\,\text{fb}^{-1}$ and $2.0\,\text{fb}^{-1}$ recorded at the centre-of-mass energies of 7 TeV and 8 TeV, respectively. The $CP$-violating asymmetry $a_{CP}^{T\text{-odd}}$ is measured to be $(0.18\pm 0.29\text{(stat)}\pm 0.04\text{(syst)})\%$. Searches for $CP$ violation in different regions of phase space of the four-body decay, and as a function of the $D^0$ decay time, are also presented. No significant deviation from the $CP$ conservation hypothesis is found.
Measurement of the ratio of three-jet to two-jet cross sections in pp¯ collisions at s=1.96 TeV
2013
We present a measurement of the ratio of multijet cross sections in pp-bar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the PYTHIA event generator do not agree with the data, while SHERPA provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, correcte…
Bounds on an Anomalous Dijet Resonance inW+jetsProduction inpp¯Collisions ats=1.96 TeV
2011
We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a $W$ boson in data corresponding to an integrated luminosity of 4.3 fb$^{-1}$ collected with the D0 detector at $\sqrt{s} =1.96$ TeV. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to 170 GeV/$c^2$. The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at 145 GeV/$c^2$ is $8\times 10^{-6}$.
Observation of the suppressed ADS modes B±→[π±K∓π+π−]DK± and B±→[π±K∓π+π−]Dπ±
2013
An analysis of and B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays is presented where the D meson is reconstructed in the four-body final state K-+/-pi(-/+)pi(+)pi(-). Using LHCb data corresponding to an integrated luminosity of 1.0 fb(-1), first observations are made of the suppressed ADS modes B-+/- ->[pi K-+/-(-/+)pi(+)pi(-)](D)K-+/- and B +/- -> [pi K-+/-(-/+)pi(+)pi(-)](D)pi(+/-) with a significance of 5.1 sigma and greater than 10 sigma, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B-+/- -> DK +/- amplitudes is determined to be r(B)(K) …
Measurement of the ratio ofBc+branching fractions toJ/ψπ+andJ/ψμ+νμfinal states
2014
The first measurement that relates semileptonic and hadronic decay rates of the B-c(+) meson is performed using proton-proton collision data corresponding to 1.0 fb(-1) of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, B(B-c(+) -> J/psi pi(+))/B(B-c(+) -> J/psi mu(+)nu(mu)) = 0.0469 +/- 0.0028(stat) +/- 0.0046(syst), is at the lower end of available theoretical predictions.
Search for flavor changing neutral currents via quark–gluon couplings in single top quark production using 2.3 fb−1 of pp¯ collisions
2010
We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb(-1) of integrated luminosity collected with the DO detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma(tgu) gu) gc) < 3.9 x 10(-3).
Measurement of the dijet invariant mass cross section in pp¯ collisions at s=1.96 TeV
2010
The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity (y_{max}) of the two jets with the largest transverse momentum in an event is measured in proton anti-proton collisions at sqrt{s} = 1.96$ TeV using 0.7 fb^{-1} of data collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to |y|=2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data.
Measurement of the Semileptonic Charge Asymmetry usingBs0→DsμXDecays
2013
We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of B{sub s}{sup 0} mesons that have undergone flavor mixing, a{sub sl}{sup s}, using B{sub s}{sup 0} ({bar B}{sub s}{sup 0}) {yields} D{sub s}{sup {-+}} {mu}{sup {+-}} X decays, with D{sub s}{sup {-+}} {yields} {phi}{pi}{sup {-+}} and {phi} {yields} K{sup +}K{sup -}, using 10.4 fb{sup -1} of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated D{sub s}{sup -} and D{sub s}{sup +} mass distributions of the B{sub s}{sup 0} and {bar B}{sub s}{sup 0} candidates yields the flavor-specif…
Measurement of the differential cross sectiondσ/dtin elasticpp¯scattering ats=1.96 TeV
2012
We present a measurement of the elastic differential cross section $d\sigma(p\bar{p}\rightarrow p\bar{p})/dt$ as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of $\approx 31 nb^{-1}$ collected with the D0 detector using dedicated Tevatron $p\bar{p} $ Collider operating conditions at sqrt(s) = 1.96 TeV and covers the range $0.26 <|t|< 1.2 GeV^2$. For $|t|<0.6 GeV^2$, d\sigma/dt is described by an exponential function of the form $Ae^{-b|t|}$ with a slope parameter $ b = 16.86 \pm 0.10(stat) \pm 0.20(syst) GeV^{-2}$. A change in slope is observed at $|t| \approx 0.6 GeV^2$, followed by a more gradual |t| dependence with increasing …
Search for neutral Higgs bosons in the multi-b-jet topology in 5.2 fb−1 of pp¯ collisions at s=1.96 TeV
2011
Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2fb-1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.
First study of the CP-violating phase and decay-width difference in Bs0→ψ(2S)ϕ decays
2016
A time-dependent angular analysis of Bs0→ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb−1 collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the Bs0 system are measured to be ϕs=0.23−0.28+0.29±0.02rad and ΔΓs=0.066−0.044+0.041±0.007ps−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the ψ(2S) resonance.
Measurement of theWboson helicity in top quark decays using5.4 fb−1ofpp¯collision data
2011
We present a measurement of the helicity of the W boson produced in top quark decays using t{bar t} decays in the {ell}+jets and dilepton final states selected from a sample of 5.4 fb{sup -1} of collisions recorded using the D0 detector at the Fermilab Tevatron p{bar p} collider. We measure the fractions of longitudinal and right-handed W bosons to be f{sub 0} = 0.669 {+-} 0.102 [{+-}0.078 (stat.) {+-} 0.065 (syst.)] and f{sub +} = 0.023 {+-} 0.053 [{+-}0.041 (stat.){+-}0.034 (syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f{sub 0} fixed to the value from the standard model yields f{sub +} = 0.010 {+-} 0.037 [{+-}0.022 (stat.) {…
Observation of Two NewΞb−Baryon Resonances
2015
Two structures are observed close to the kinematic threshold in the Ξb0π- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity JP=(1/2)+ and JP=(3/2)+ states, denoted Ξb′- and Ξb∗-. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(Ξb′-)-m(Ξb0)-m(π-)=3.653±0.018±0.006MeV/c2, m(Ξb∗-)-m(Ξb0)-m(π-)=23.96±0.12±0.06MeV/c2, Γ(Ξb∗-)=1.65±0.31±0.10MeV, where the first and second uncertainties are statistical and systema…
Search for a heavy neutral gauge boson in the dielectron channel with 5.4 fb−1 of pp¯ collisions at s=1.96 TeV
2011
We report the results of a search for a heavy neutral gauge boson Z' decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95 sigma(p (p) over bar -> Z') x BR(Z' -> ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for bosons in a variety of models. For the sequential standard model boson a lower mass limit of 1023 GeV is obtained.
Measurement of Z/γ∗+jet+X angular distributions in pp¯ collisions at s=1.96 TeV
2010
We present the first measurements at a hadron collider of differential cross sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and |y_boost(Z, jet)|. Vector boson production in association with jets is an excellent probe of QCD and constitutes the main background to many small cross section processes, such as associated Higgs production. These measurements are crucial tests of the predictions of perturbative QCD and current event generators, which have varied success in describing the data. Using these measurements as inputs in tuning event generators will increase the experimental sensitivity to rare signals.
Measurement ofsin2θeffℓandZ-light quark couplings using the forward-backward charge asymmetry inpp¯→Z/γ*→e+e−events withL=5.0 fb−1ats=1.96 TeV
2011
We measure the mass dependence of the forward-backward charge asymmetry in 157,553 $p\bar{p} \rightarrow Z/\gamma^{*} \rightarrow e^+e^-$ interactions, corresponding to 5.0 fb$^{-1}$ of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider at $\sqrt{s}=1.96$ TeV. The effective weak mixing angle ($\sin^2\theta_{eff}^{lept}$) from this process involving predominantly the first generation of quarks is extracted as $\sin^2\theta_{eff}^{lept} = 0.2309 \pm 0.0008 ({stat.}) \pm 0.0006 ({syst.})$. We also present the most precise direct measurement of the vector and axial-vector couplings of $u$ and $d$ quarks to the $Z$ boson.
Measurements of charm mixing and CP violation using D0→K±π∓ decays
2017
Measurements of charm mixing and CP violation parameters from the decay-time-dependent ratio of D0→K+π− to D0→K−π+ decay rates and the charge-conjugate ratio are reported. The analysis uses B¯¯¯¯→D∗+μ−X, and charge-conjugate decays, where D∗+→D0π+, and D0→K∓π±. The pp collision data are recorded by the LHCb experiment at center-of-mass energies s√ = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. The data are analyzed under three hypotheses: (i) mixing assuming CP symmetry, (ii) mixing assuming no direct CP violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct CP violation and/or CP violation in the superpos…
Search for W′→tb resonances with left- and right-handed couplings to fermions
2011
We present a search for the production of a heavy gauge boson, W', that decays to third-generation quarks, by the D0 Collaboration in ppbar collisions at sqrt(s)= 1.96 TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W' boson to fermions. For couplings with the same strength as the standard model W boson, we set the following limits for M(W') > m(nu_R): M(W')>863 GeV for purely left-handed couplings, M(W')>885 GeV for purely right-handed couplings, and M(W')>916 GeV if both left- and right-handed couplings are present. The limit for r…
b-Jet identification in the D0 experiment
2010
Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p-pbar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.
Search for charged massive long-lived particles ats=1.96 TeV
2013
We present a search for charged massive long-lived particles (CMLLPs) that are pair produced in p-pbar collisions at sqrt(s)= 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. Our result is a combination of two searches where either one or both CMLLPs are reconstructed in the detector. We select events with muon-like particles that have both speed and ionization energy loss dE/dx different from muons produced in p-pbar collisions. In the absence of evidence for CMLLPs corresponding to 6.3 fb-1 of integrated luminosity, we set limits on the CMLLP masses in several supersymmetric models, excluding masses below 278 GeV for long-lived gaugino-like charginos, and masses …
Search for single top quarks in the tau + jets channel using 4.8 fb−1 of pp¯ collision data
2010
We present the first direct search for single top quark production using tau leptons. The search is based on 4.8 fb$^{-1}$ of integrated luminosity collected in $p\bar{p}$ collisions at $\sqrt{s}$=1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We select events with a final state including an isolated tau lepton, missing transverse energy, two or three jets, one or two of them $b$ tagged. We use a multivariate technique to discriminate signal from background. The number of events observed in data in this final state is consistent with the signal plus background expectation. We set in the tau+jets channel an upper limit on the single top quark cross section of \TauLimObs pb …
Measurement of the effective Bs0→K+K− lifetime
2012
A precise determination of the effective $B_s^0 \rightarrow K^+ K^-$ lifetime can be used to constrain contributions from physics beyond the Standard Model in the $B_s^0$ meson system. Conventional approaches select $B$ meson decay products that are significantly displaced from the $B$ meson production vertex. As a consequence, $B$ mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb$^{-1}$ of data recorded by the LHCb experiment, the effective $B_s^0 \rightarrow K^+ K^-$ lifetime is meas…
Evidence for aBs0π±State
2016
Made available in DSpace on 2022-04-28T19:03:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-07-07 We report evidence for a narrow structure, X(5568), in the decay sequence X(5568)→Bs0π±, Bs0→J/ψφ, J/ψ→μ+μ-, φ→K+K-. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m=5567.8±2.9(stat)-1.9+0.9(syst) MeV/c2 and Γ=21.9±6.4(stat)-2.5+5.0(syst) MeV/c2. If the decay is X(5568)→Bs∗π±→Bs0γπ± with an unseen γ, m(X(5568)) will be shifted up by m(Bs∗)-m(Bs0)∼49 MeV/c2. This measurement is based on 10.4 fb-1 of pp collision data at s=1.96 TeV collected by the D0 experiment at th…