0000000001049129
AUTHOR
Marcin Chrzaszcz
First observation of the doubly charmed baryon decay Ξcc++→Ξc+π+
The doubly charmed baryon decay Ξcc++→Ξc+π+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λc+K−π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7 fb−1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξcc++ mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξc+) MeV/c2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be [B(Ξcc++→Ξc+π+)×B(Ξc+→pK−π+)]/[B(Ξcc++→Λc+K−π+π+)×B(Λc+→pK−π+)]=0.035±0.009(stat)±0.003(syst).
Model-Independent Evidence forJ/ψpContributions toΛb0→J/ψpK−Decays
The data sample of Lambda(0)(b) -> J/psi pK(-) decays acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb(-1), is inspected for the presence of J/psi p or J/psi K- contributions with minimal assumptions about K(-)p contributions. It is demonstrated at more than nine standard deviations that Lambda(0)(b) -> J/psi pK(-) decays cannot be described with K- p contributions alone, and that J/psi K- contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for P-c(+)-> J/psi p charmonium-pentaquark states in the same data sample.
Search for Long-Lived Particles ine+e−Collisions
We present a search for a neutral, long-lived particle L that is produced in e^+e^− collisions and decays at a significant distance from the e^+e^− interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e^+e^− data sample with a luminosity of 489.1 fb^(−1) collected by the BABAR detector at the Υ(4S), Υ(3S), and Υ(2S) resonances and just below the Υ(4S). Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible two-body L decay modes …
First observation of the rareB+→D+K+π−decay
The B+→D+K+π- 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. The signal significance is 8σ and the branching fraction is measured to be B(B+→D+K+π-)=(5.31±0.90±0.48±0.35)×10-6, where the uncertainties are statistical, systematic and due to the normalization mode B+→D-K+π+, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from B+→D2∗(2460)0K+ and B+→D+K∗(892)0 decays. No significant signals are observed and upper limits are set on their branching fractions.
First Evidence for cos2β>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity
We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] p…
First experimental study of photon polarization in radiative B0s decays.
The polarization of photons produced in radiative $B^{0}_{s}$ decays is studied for the first time. The data are recorded by the LHCb experiment in $pp$ collisions corresponding to an integrated luminosity of 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} \to \phi \gamma$ decay rate is conducted to determine the parameter ${\mathcal{A}}^\Delta$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b \to s \gamma$ transitions. A value of ${\mathcal{A}}^\Delta=-0.98^{\,+0.46\,+0.23}_{\,-0.52\,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviatio…
Search for CP violation inD0→π−π+π0decays with the energy test
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 the baryonic decayB¯0→Λc+p¯K−K+
We report the observation of the baryonic decay B^0 → Λ^+_c pK^−K^+ using a data sample of 471×10^6 BB pairs produced in e^+e^− annihilations at √s = 10.58 GeV. This data sample was recorded with the BABAR detector at the PEP-II storage ring at SLAC. We find B(B^0 → Λ^+_c pK^−K^+)=(2.5±0.4_((stat))±0.2_((syst))± 0.6_(B(Λ^+_c)))×10^(−5), where the uncertainties are statistical, systematic, and due to the uncertainty of the Λ^+_c →p K^−π^+ branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay B^0 → Λ^+_c pϕ, we determine the upper limit B(B^0 → Λ^+_c pϕ) <1.2 × 10^(−5) at 90% confidence le…
Measurement of theI=1/2Kπ S-wave amplitude from Dalitz plot analyses ofηc→KK¯πin two-photon interactions
We study the processes γγ→K^0_SK^±π^∓ and γγ→K^+K^−π^0 using a data sample of 519 fb^(−1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e− collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. We observe ηc decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I=1/2 Kπ S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c^2. In contrast, the amplitudes show very marked…
Study of thee+e−→K+K−reaction in the energy range from 2.6 to 8.0 GeV
The e^+e^− → K^+K^− cross section and charged-kaon electromagnetic form factor are measured in the e^+e^− center-of-mass energy range (E) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb^(−1) of data collected with the BABAR detector at the PEP-II2 e^+e^− collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than 1/E^2 and approaches the asymptotic QCD prediction. Production of the K^+K^− final state through the J/ψ and ψ(2S) intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a mod…
Studies of the resonance structure inD0→KS0K±π∓decays
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…
Dalitz plot analyses ofB0→D−D0K+andB+→D¯0D0K+decays
We present Dalitz plot analyses for the decays of B mesons to D^−D^0K^+ and D^0D^0K^+. We report the observation of the D^∗_(s1)(2700)^+ resonance in these two channels and obtain measurements of the mass M(D^∗_(s1)(2700)+)=2699^(+14)_(−7) MeV/c^2 and of the width Γ(D^∗_(s1)(2700)+)=127^(+24)_(−19) MeV, including statistical and systematic uncertainties. In addition, we observe an enhancement in the D^0K^+ invariant mass around 2350–2500 MeV/c^2 in both decays B^0→D^−D^0K^+ and B^+→D^0D^0K^+, which we are not able to interpret. The results are based on 429 fb^(−1) of data containing 471×10^6BB pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerato…
Measurement of the Ratio of Branching FractionsB(B¯0→D*+τ−ν¯τ)/B(B¯0→D*+μ−ν¯μ)
The branching fraction ratio R(D-*) = B((B) over bar (0) -> D-*(+)tau(-)(nu) over bar (tau))/B((B) over bar (0) -> D-*(+)mu(-)(nu) over bar (mu)) is measured using a sample of proton-proton collision data corresponding to 3.0 fb(-1) of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode tau(-) -> mu(-)(nu) over bar (mu)nu(tau). The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate (B) over bar (0) decays gives R(D-*) =…
Search for B+→K+τ+τ− at the BaBar Experiment
We search for the rare flavor-changing neutral current process B^{+}→K^{+}τ^{+}τ^{-} using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the ϒ(4S) resonance, corresponds to a total integrated luminosity of 424 fb^{-1} and to 471×10^{6} BB[over ¯] pairs. We reconstruct one B meson, produced in the ϒ(4S)→B^{+}B^{-} decay, in one of many hadronic decay modes and search for activity compatible with a B^{+}→K^{+}τ^{+}τ^{-} decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria,…
Search for weakly decaying b -flavored pentaquarks
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 $\Lambda_b$.
Measurement of the B0→D*−π+π−π+ branching fraction
Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x 10^-3, where the first uncertainty is statistical and the second is systematic. Our measurement will be helpful in studies of lepton universality by measuring B(B^0 -> D^*- tau^+ nu_tau) using tau^+ -> pi^+ pi^- pi^+ nu-bar_tau decays, normalized to B(B^0 -> D^*- pi^+ pi^- pi^+.
Study ofB±,0→J/ψK+K−K±,0and search forB0→J/ψϕatBaBar
We study the rare B meson decays B{+-,0} --> J/\psi\ K^+ K^- K{+-,0}, B{+-,0} --> J/\psi\ \phi\ K{+-,0}, and search for B0 --> J/\psi\ \phi, using 469 million BBbar events collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II e+e- asymmetric-energy collider. We present new measurements of branching fractions and a study of the J/\psi\phi mass distribution in search of new charmonium-like states. In addition, we search for the decay B0 --> J/\psi\ \phi, and find no evidence of a signal.
Measurement of CP asymmetries in two-body B(s)0 -meson decays to charged pions and kaons
The time-dependent CP asymmetries in B0→π+π− and B0s→K+K− decays are measured using a data sample of p p collisions 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. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π− and B0s→π+K− decays. The results are Cπ+π−=−0.34±0.06±0.01, Sπ+π−=−0.63±0.05±0.01, CK+K−=0.20±0.06±0.02, SK+K−=0.18±0.06±0.02, AΔΓK+K−=−0.79±0.07±0.10, AB0CP=−0.084±0.004±0.003, and AB0sCP=0.213±0.015±0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the B0s→K+K− decay for the first time.
Search for a light Higgs resonance in radiative decays of theϒ(1S)with a charm tag
A search is presented for the decay Υ(1S)→ γA^0, A^0 → cc[bar], where A^0 is a candidate for the CP-odd Higgs boson of the next-to-minimal supersymmetric standard model. The search is based on data collected with the BABAR detector at the Υ(2S) resonance. A sample of Υ(1S) mesons is selected via the decay Υ(2S)→π + π − Υ(1S). The A^0 → cc[bar] decay is identified through the reconstruction of hadronic D^0, D^+, and D^∗ (2010)^+ meson decays. No significant signal is observed. The measured 90% confidence-level upper limits on the product branching fraction B(Υ(1S) → γA^0 ) × B(A^0 → cc[bar] ) range from 7.4×10^(−5) to 2.4×10^(−3) for A^0 masses from 4.00 to 8.95 GeV/c^2 and 9.10 to 9.25 Ge…
Measurement of the branching fraction of the decay Bs0→KS0KS0
A measurement of the branching fraction of the decay Bs0→KS0KS0 is performed using proton-proton collision data corresponding to an integrated luminosity of 5 fb-1 collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be B(Bs0→KS0KS0)=[8.3±1.6(stat)±0.9(syst)±0.8(norm)±0.3(fs/fd)]×10-6, where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode B0→φKS0 and the ratio of hadronization fractions fs/fd. This is the most precise measurement of this branching fraction to date. Furthermore, a measurement of the branching fraction of the decay B0…
Measurement of the c0 Baryon Lifetime
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, …
First Observation ofCPViolation inB¯0→DCP(*)h0Decays by a Combined Time-Dependent Analysis ofBABARand Belle Data
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) an…
Observation of the rare B(s)(0) + decay from the combined analysis of CMS and LHCb data.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported licence.-- et al.
Amplitude analysis ofB+→J/ψϕK+decays
The first full amplitude analysis of B+→J/ψϕK+ with J/ψ→μ+μ−, ϕ→K+K− decays is performed with a data sample of 3 fb−1 of pp collision data collected at s√=7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK+, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest is best described as a D±sD∗∓s cusp, but a resonant interpretation is also possible with mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state. The mode…
Measurement of the Difference of Time-IntegratedCPAsymmetries inD0→K−K+andD0→π−π+Decays
A search for CP violation in $D^0 \rightarrow K^{-} K^{+} $ and $D^0 \rightarrow \pi^{-} \pi^{+} $ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of $3~fb^{-1}$, collected using the LHCb detector at centre-of-mass energies of 7 and $8~$TeV. The flavour of the charm meson is inferred from the charge of the pion in $D^{*+}\rightarrow D^0\pi^+$ and $D^{*-}\rightarrow \bar{D^0}\pi^{-}$ decays. The difference between the CP asymmetries in $D^0 \rightarrow K^{-} K^{+} $ and $D^0 \rightarrow \pi^{-} \pi^{+} $ decays, $\Delta A_{CP} \equiv A_{CP}(K^{-} K^{+}) - A_{CP}(\pi^{-} \pi^{+})$, is measured to be $\left( -0.10 \pm 0.08(stat) \pm 0.03(syst) \right) \…
Measurement of the W boson mass
The W boson mass is measured using proton-proton collision data at root s = 13 TeV corresponding to an integrated luminosity of 1.7fb(-1) recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q/p(T) distribution of a sample of W ->mu y decays and the phi* distribution of a sample of Z -> mu mu decays the W boson mass is determined to be
Amplitude analysis ofB−→D+π−π−decays
The Dalitz plot analysis technique is used to study the resonant substructures of $B^{-} \to D^{+} \pi^{-} \pi^{-}$ decays in a data sample corresponding to 3.0 ${\rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high $D^{+}\pi^{-}$ mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the $D^{+}\pi^{-}$ S-wave together with virtual contributions from the $D^{*}(2007)^{0}$ and $B^{*0}$ states, and components corresponding to the $D^{*}_{2}(2460)^{0}$, $D^{*}_{1}(2680)^{0}$, $D^{*}_…
Observation of Bc+→J/ψD(*)K(*) decays
A search for the decays B + c → J / ψ D ( * ) 0 K + and B + c → J / ψ D ( * ) + K * 0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb − 1 . The decays B + c → J / ψ D 0 K + and B + c → J / ψ D * 0 K + are observed for the first time, while first evidence is reported for the B + c → J / ψ D * + K * 0 and B + c → J / ψ D + K * 0 decays. The branching fractions of these decays are determined relative to the B + c → J / ψ π + decay. The B + c mass is measured, using the J / ψ D 0 K + final state, to be 6274.28 ± 1.40 ( stat ) ± 0.32 ( syst ) MeV / c 2 . This is the most precise single measurement of the B + c mass to date.
Study of J/ψ Production in Jets
The production of $J/\psi$ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the $J/\psi$ meson, $z \equiv p_{\rm T}(J/\psi)/p_{\rm T}({\rm jet})$, is measured using jets with $p_{\rm T}({\rm jet}) > 20$ GeV in the pseudorapidity range $2.5 < \eta({\rm jet}) < 4.0$. The observed $z$ distribution for $J/\psi$ mesons produced in $b$-hadron decays is consistent with expectations. However, the results for prompt $J/\psi$ production do not agree with predictions based on fixed-order non-relativistic QCD. This is the first measurement o…
Study ofCPAsymmetry inB0−B¯0Mixing with Inclusive Dilepton Events
We present a measurement of the asymmetry A_{CP} between same-sign inclusive dilepton samples l^{+}l^{+} and l^{-}l^{-} (l=e, μ) from semileptonic B decays in ϒ(4S)→BB[over ¯] events, using the complete data set recorded by the BABAR experiment near the ϒ(4S) resonance, corresponding to 471×10^{6} BB[over ¯] pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B[over ¯]^{0}→B^{0}) and P(B^{0}→B[over ¯]^{0}), and therefore probes CP and T violation. The result, A_{CP}=[-3.9±3.5(stat)±1.9(syst)]×10^{-3}, is consistent with the standard model expectation.
Measurement of initial-state–final-state radiation interference in the processese+e−→μ+μ−γande+e−→π+π−γ
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interfe…