Search for a Standard Model Higgs Boson inWH→ℓvbb¯inpp¯Collisions ats=1.96  TeV

We present a search for a standard model Higgs boson produced in association with a W boson using 2.7 fb(-1) of integrated luminosity of pp collision data taken at square root s = 1.96 TeV. Limits on the Higgs boson production rate are obtained for masses between 100 and 150 GeV/c(2). Through the use of multivariate techniques, the analysis achieves an observed (expected) 95% confidence level upper limit of 5.6 (4.8) times the theoretically expected production cross section for a standard model Higgs boson with a mass of 115 GeV/c(2).

Search for the Higgs Boson in theH→WW(*)→l+νl−ν¯Decay Channel inppCollisions ats=7  TeVwith the ATLAS Detector

A search for the Higgs boson has been performed in the H -> WW(*()) -> l+vl-(v) over bar channel (l = e/mu) with an integrated luminosity of 2.05 fb(-1) of pp collisions at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110 GeV< m(H) < 300 GeV. The observations exclude the presence of a standard model Higgs boson with a mass 145 < m(H) < 206 GeV at 95% confidence level.

Search for new phenomena in the WW→lνl′ν′ final state in pp collisions at s=7TeV with the ATLAS detector

This Letter reports a search for a heavy particle that decays to WW using events produced in pp collisions at root s = 7 TeV. The data were recorded in 2011 by the ATLAS detector and correspond to an integrated luminosity of 4.7 fb(-1). WW -> lvl'v' (l,l' = e or mu) final states are considered and the distribution of the transverse mass of the W W candidates is found to be consistent with Standard Model expectations. Upper limits on the production cross section times branching ratio into W boson pairs are set for Randall-Sundrum and bulk Randall-Sundrum gravitons, which result in observed 95% CL lower limits on the masses of the two particles of 1.23 TeV and 0.84 TeV, respectively.

Search for contact interactions and large extra dimensions in dilepton events fromppcollisions ats=7  TeVwith the ATLAS detector

A search for nonresonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at root s = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb(-1) in the e(+)e(-) and mu(+)mu(-) channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence level lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in…

Search for Standard Model Higgs Boson Production in Association with a W Boson at CDF

We present a search for the standard model Higgs boson production in association with a W boson in proton-antiproton collisions (pp̅ →W±H→ℓνbb̅ ) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 2.7  fb-1. We recorded this data with two kinds of triggers. The first kind required high-pT charged leptons and the second required both missing transverse energy and jets. The search selects events consistent with a signature of a single lepton (e±/μ±), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a…

Combined Tevatron upper limit ongg→H→W+W−and constraints on the Higgs boson mass in fourth-generation fermion models

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.

Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events frompp¯Collisions ats=1.96  TeV

We present the results of a search for pair production of the supersymmetric partner of the top quark (the top squark (t) over tilde (1)) decaying to a b quark and a chargino (chi) over tilde (+/-)(1) with a subsequent (chi) over tilde (+/-)(1) decay into a neutralino (chi) over tilde (0)(1), lepton l, and neutrino nu Using a data sample corresponding to 2.7 fb(-1) of integrated luminosity of p (p) over bar collisions at root s = 1: 96 TeV collected by the CDF II detector, we reconstruct the mass of top squark candidate events and fit the observed mass spectrum to a combination of standard model processes and (t) over tilde (1)(t) over tilde (1). We find no evidence for (t) over tilde (1)(t…

Direct Measurement of theWProduction Charge Asymmetry inpp¯Collisions ats=1.96  TeV

We wish to thank R.S. Thorne and W.J. Stirling for useful discussions on the theoretical predictions.We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the Korean Science…

Search for New Phenomena intt¯Events with Large Missing Transverse Momentum in Proton-Proton Collisions ats=7  TeVwith the ATLAS Detector

A search for new phenomena in tt events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04  fb-1 of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb …

Updated Search for the Flavor-Changing Neutral-Current Decay D^0 \to {\mu} + {\mu}-

We report on a search for the flavor-changing neutral-current decay D0 \to {\mu}+ {\mu}- in pp collisions at \surd s = 1.96 TeV using 360 pb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D0 candidates in the {\mu}+ {\mu}-, {\pi}+{\pi}-, and K-{\pi}+ decay modes. We use the Cabibbo-favored D0 \to K-{\pi}+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D0 \to{\pi}+ {\pi}- channel for normalization. We set an upper limit on the branching fraction (D0 --> {\mu}+ {\mu}-) < 2.1 E-7 (3.0 E-7) at the 90% (95%) confidence level.

Direct Bound on the Total Decay Width of the Top Quark inpp¯Collisions ats=1.96  TeV

We present the first direct experimental bound on the total decay width of the top quark, Gamma(t), using 955 pb(-1) of the Tevatron's p (p) over bar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of Gamma(t) < 13.1 GeV for an assumed top quark mass of 175 GeV/c(2).

Measurement of the azimuthal anisotropy for charged particle production insNN=2.76TeV lead-lead collisions with the ATLAS detector

Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at root sNN = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 mu b(-1). This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients v(n) denoting the magnitude of the anisotropy. Significant v(2)-v(6) values are obtained as a function of transverse momentum (0.5 = 3 are found to vary weakly with both eta and centrality, and their p(T) dependencies are found to follow an approximate scaling relation, v(n)(1/n)(p(T)) proportional …

Search for High-Masse+e−Resonances inpp¯Collisions ats=1.96  TeV

We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions. This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foundation; the A.P. Sloan Foundation; the Bundesministerium fur Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Science and Technology Facilities…

Measurement of charged-particle event shape variables in inclusive(s)=7  TeVproton-proton interactions with the ATLAS detector

The measurement of charged-particle event shape variables is presented in inclusive inelastic pp collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles' momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented.…

Search forWWandWZResonances Decaying to Electron, MissingET, and Two Jets inpp¯Collisions ats=1.96  TeV.

We present a search for WW and WZ production in final states that contain a charged lepton (electron or muon) and at least two jets, produced in {radical}(s)=1.96 TeV pp collisions at the Fermilab Tevatron, using data corresponding to 1.2 fb{sup -1} of integrated luminosity collected with the CDF II detector. Diboson production in this decay channel has yet to be observed at hadron colliders due to the large single W plus jets background. An artificial neural network has been developed to increase signal sensitivity, as compared with an event selection based on conventional cuts. We set a 95% confidence level upper limit of {sigma}{sub WW}xBR(W{yields}l{nu}{sub l},W{yields}jets)+{sigma}{sub…

Measurement of theW+W−Cross Section ins=7  TeVppCollisions with ATLAS

This Letter presents a measurement of the W+W- production cross section in root s = 7 TeV pp collisions by the ATLAS experiment, using 34 pb(-1) of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected background of 1.7 +/- 0.6 events. The measured cross section is 41(-16)(+20)(stat) +/- 5(syst) +/- 1(lumi) pb, which is consistent with the standard model prediction of 44 +/- 3 pb calculated at next-to-leading order in QCD.

Study of jets produced in association with aWboson inppcollisions ats=7  TeVwith the ATLAS detector

We report a study of final states containing a W boson and hadronic jets, produced in proton-proton collisions at a center-of-mass energy of 7 TeV. The data were collected with the ATLAS detector at the CERN LHC and comprise the full 2010 data sample of 36 pb^-1. Cross sections are determined using both the electron and muon decay modes of the W boson and are presented as a function of inclusive jet multiplicity, N_jet, for up to five jets. At each multiplicity, cross sections are presented as a function of jet transverse momentum, the scalar sum of the transverse momenta of the charged lepton, missing transverse momentum, and all jets, the invariant mass spectra of jets, and the rapidity d…

Measurement of theb-hadron production cross section using decays toμ−D0Xfinal states inpp¯collisions ats=1.96  TeV

We report a measurement of the production cross section for b hadrons in p{bar p} collisions at {radical}s = 1.96 TeV. Using a data sample derived from an integrated luminosity 83 pb{sup -1} collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron, we analyze b hadrons, H{sub b}, partially reconstructed in the semileptonic decay mode H{sub b} {yields} {mu}{sup -} D{sup 0} X. Our measurement of the inclusive production cross section for b hadrons with transverse momentum p{sub T} > 9 GeV/c and rapidity |y| < 0.6 is {sigma} = 1.30 {micro}b {+-} 0.05 {micro}b(stat) {+-} 0.14 {micro}b(syst) {+-} 0.07 {micro}b({Beta}), where the uncertainties are statistical, systematic, a…

Search forR-Parity Violating Decays of Sneutrinos toeμ,μτ, andeτPairs inpp¯Collisions ats=1.96  TeV

7 paginas, 2 figuras, 3 tablas.-- PACS numbers: 14.80.Ly, 12.60.Jv, 13.85.Qk, 14.60.St.--CDF Collaboration: et al.

Measurement of the fraction oftt¯production via gluon-gluon fusion inpp¯collisions ats=1.96  TeV

We present a measurement of the ratio of the tt production cross section via gluon-gluon fusion to the total tt production cross section in pp collisions at √s=1.96  TeV at the Tevatron. Using a data sample with an integrated luminosity of 955  pb-1 recorded by the CDF II detector at Fermilab, we select events based on the tt decay to lepton+jets. Using an artificial neural network technique we discriminate between tt events produced via qq annihilation and gg fusion, and find Gf=σ(gg→tt )/σ(pp →tt )<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most stringent measurement of this quantity by CDF to date, Gf=0.07-0.07+0.15.

Measurements of the pseudorapidity dependence of the total transverse energy in proton-proton collisions at sqrt(s) = 7 TeV with ATLAS

This paper describes measurements of the sum of the transverse energy of particles as a function of particle pseudorapidity, η, in proton-proton collisions at a centre-of-mass energy, √s = 7 TeV using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region |η| < 4.8 for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum. In the second dataset measurements are made in the region transverse to the hard scatter. The distributions are compared to the predictions of various Monte Carlo event generators, which generally tend to underestimate the amoun…

Search for Supersymmetry inpp¯Collisions ats=1.96  TeVUsing the Trilepton Signature for Chargino-Neutralino Production

We use the three lepton and missing energy trilepton signature to search for chargino-neutralino production with 2.0 fb(-1) of integrated luminosity collected by the CDF II experiment at the Tevatron p (p) over bar collider. We expect an excess of approximately 11 supersymmetric events for a choice of parameters of the mSUGRA model, but our observation of 7 events is consistent with the standard model expectation of 6.4 events. We constrain the mSUGRA model of supersymmetry and rule out chargino masses up to 145 GeV/c(2) for a specific choice of parameters.

Search for the Associated Production of the Standard-Model Higgs Boson in the All-Hadronic Channel

We report on a search for the standard-model Higgs boson in pp collisions at s=1.96 TeV using an integrated luminosity of 2.0 fb(-1). We look for production of the Higgs boson decaying to a pair of bottom quarks in association with a vector boson V (W or Z) decaying to quarks, resulting in a four-jet final state. Two of the jets are required to have secondary vertices consistent with B-hadron decays. We set the first 95% confidence level upper limit on the VH production cross section with V(-> qq/qq('))H(-> bb) decay for Higgs boson masses of 100-150 GeV/c(2) using data from run II at the Fermilab Tevatron. For m(H)=120 GeV/c(2), we exclude cross sections larger than 38 times the standard-m…

Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton ins=7  TeVpp collisions using1  fb−1of ATLAS data

We present an update of a search for supersymmetry in final states containing jets, missing transverse momentum, and one isolated electron or muon, using 1.04 fb(-1) of proton-proton collision data at root s =7 TeV recorded by the ATLAS experiment at the LHC in the first half of 2011. The analysis is carried out in four distinct signal regions with either three or four jets and variations on the (missing) transverse momentum cuts, resulting in optimized limits for various supersymmetry models. No excess above the standard model background expectation is observed. Limits are set on the visible cross section of new physics within the kinematic requirements of the search. The results are inter…

Search for a Standard Model Higgs Boson in theH→ZZ→ℓ+ℓ−νν¯Decay Channel with the ATLAS Detector

A search for a heavy standard model Higgs boson decaying via H -> ZZ -> l(+)l(-)v (v) over bar, where l = e, mu, is presented. It is based on proton-proton collision data at root s = 7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340 < m(H) < 450 GeV at the 95% confiden…

Evidence for a Particle Produced in Association with Weak Bosons and Decaying to a Bottom-Antibottom Quark Pair in Higgs Boson Searches at the Tevatron

Aaltonen, T. et al.

Combination of Tevatron searches for the standard model Higgs boson in the W+W- decay mode.

11 páginas, 4 figuras, 1 tabla.-- CDF Collaboration: et al.

Search fortbResonances in Proton-Proton Collisions ats=7  TeVwith the ATLAS Detector

This Letter presents a search for tb resonances in 1.04 fb(-1) of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected standard model backgrounds. The model of a right-handed W(R)' with standard model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in the data, and upper limits on the cross section times the branching ratio of W(…

Search for high-mass states with one lepton plus missing transverse momentum in proton–proton collisions at s=7 TeV with the ATLAS detector

The ATLAS detector is used to search for high-mass states, such as heavy charged gauge bosons (W', W*) decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 36 pb-1. No excess beyond standard model expectations is observed. A W' with sequential standard model couplings is excluded at 95% confidence level for masses below 1.49 TeV, and a W*(charged chiral boson) for masses below 1.47 TeV.

Search for a Heavy Toplike Quark inpp¯Collisions ats=1.96  TeV

We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb(-1) collected by the CDF II detector in pp collisions at √s=1.96 TeV. We perform parallel searches for t'→Wb and t'→Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t' quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c(2) at 95% C.L.

Measurement of theWW+WZProduction Cross Section Using thelepton+jetsFinal State at CDF II

We report two complementary measurements of the diboson (WW + WZ) cross section in the final state consisting of an electron or muon, missing transverse energy, and jets, performed using p{bar p} collision data at {radical}s = 1.96 TeV collected by the Collider Detector at Fermilab. The first method uses the dijet invariant mass distribution while the second method uses more of the kinematic information in the event through matrix-element calculations of the signal and background processes and has a higher sensitivity. The result from the second method has a signal significance of 5.4{sigma} and is the first observation of WW + WZ production using this signature. Combining the results from …

Measurement of the top quark mass using the invariant mass of lepton pairs in soft muon b-tagged events

We present the first measurement of the mass of the top quark in a sample of t (t) over bar -> l (nu) over barb (b) over barq (q) over bar events (where l = e, mu) selected by identifying jets containing a muon candidate from the semileptonic decay of heavy-flavor hadrons (soft muon b tagging). The p (p) over bar collision data used correspond to an integrated luminosity of 2 fb(-1) and were collected by the CDF II detector at the Fermilab Tevatron Collider. The measurement is based on a novel technique exploiting the invariant mass of a subset of the decay particles, specifically the lepton from the W boson of the t -> Wb decay and the muon from a semileptonic b decay. We fit template hist…

Search for the decay Bs0→μ+μ− with the ATLAS detector

A blind analysis searching for the decay B-s(0) -> mu(+)mu(-) has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. W ...

Search for resonant top quark plus jet production intt¯+jetsevents with the ATLAS detector inppcollisions ats=7  TeV

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, to (t)over-barq or tq, leading to a resonance within the t(t)over-bar + jets signature. The full 2011 ATLAS pp collision data set from the LHC (4.7 fb(-1)) is used to search for t(t)over-bar events produced in association with jets, in which one of the W bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for both W' boson and color tr…

First measurement of the ratio of branching fractionsB(Λb0→Λc+μ−ν¯μ)/B(Λb0→Λc+π−)

This article presents the first measurement of the ratio of branching fractions B(Lambda(0)(b) -> Lambda(+)(c) mu(-) (nu) over bar (mu))/B(Lambda(0)(b) -> Lambda(+)(c) pi(-)). Measurements in two control samples using the same technique B((B) over bar (0) -> D+ mu(-) (nu) over bar (mu))/B((B) over bar (0) -> D+ pi(-)) and B((B) over bar (0) -> D*(2010)(+) mu(-) (nu) over bar (mu))/B((B) over bar (0) -> D*(2010)(+) pi(-)) are also reported. The analysis uses data from an integrated luminosity of approximately 172 pb(-1) of p (p) over bar collisions at root s = 1: 96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The relative branching fractions are measured to be B(Lambda(…

Measurement of the centrality dependence of the charged particle pseudorapidity distribution in lead–lead collisions at sNN=2.76 TeV with the ATLAS detector

The ATLAS experiment at the LHC has measured the centrality dependence of charged particle pseudorapidity distributions over vertical bar eta vertical bar < 2 in lead-lead collisions at a nucleo ...

Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector

A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at √s = 7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb[superscript −1]. No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles.

Search for Dark Matter Candidates and Large Extra Dimensions in Events with a Photon and Missing Transverse Momentum inppCollision Data ats=7  TeVwith the ATLAS Detector

Measurement of the isolated diphoton cross section inppcollisions ats=7  TeVwith the ATLAS detector

The ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s=7  TeV. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of 37  pb-1. The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass (mγγ), total transverse momentum (pT,γγ), and azimuthal separation (Δϕγγ), are presented and compared to the predictions of next-to-leading-order QCD.

Search for a Fermiophobic Higgs Boson Decaying into Diphotons inpp¯Collisions ats=1.96  TeV

A search for a narrow diphoton mass resonance is presented based on data from 3.0 fb{sup -1} of integrated luminosity from p{bar p} collisions at {radical}s = 1.96 TeV collected by the CDF experiment. No evidence of a resonance in the diphoton mass spectrum is observed, and upper limits are set on the cross section times branching fraction of the resonant state as a function of Higgs boson mass. The resulting limits exclude Higgs bosons with masses below 106 GeV/c{sup 2} at a 95% Bayesian credibility level (C.L.) for one fermiophobic benchmark model.

Observation of s-Channel Production of Single Top Quarks at the Tevatron

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.

Search for Pair Production of a Newb′Quark that Decays into aZBoson and a Bottom Quark with the ATLAS Detector

A search is reported for the pair production of a new quark b' with at least one b' decaying to a Z boson and a bottom quark. The data, corresponding to 2.0 fb(-1) of integrated luminosity, were co ...

Measurement of the Z→ττ cross section with the ATLAS detector

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM

Measurement of the production cross section forZ/γ*in association with jets inppcollisions ats=7  TeVwith the ATLAS detector

Results are presented on the production of jets of particles in association with a Z/gamma* boson, in proton-proton collisions at root s = 7 TeV with the ATLAS detector. The analysis includes the full 2010 data set, collected with a low rate of multiple proton-proton collisions in the accelerator, corresponding to an integrated luminosity of 36 pb(-1). Inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into electron or muon pairs, are measured for jets with transverse momentum p(T) > 30 GeV and jet rapidity vertical bar y vertical bar < 4.4. The measurements are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carl…

Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions ats=7  TeVwith the ATLAS detector

A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy root s = 7 TeV is presented. Photons are ...

Measurement of theZZProduction Cross Section and Limits on Anomalous Neutral Triple Gauge Couplings in Proton-Proton Collisions ats=7  TeVwith the ATLAS Detector

A measurement of the ZZ production cross section in proton-proton collisions at root s = 7 TeV using data corresponding to an integrated luminosity of 1.02 fb(-1) recorded by the ATLAS experiment a ...

Search for Neutral Higgs Bosons in Events with Multiple Bottom Quarks at the Tevatron

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…

Search for the supersymmetric partner of the top quark inpp¯collisions ats=1.96  TeV

We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy root s = 1: 96 TeV. This search was conducted within the framework of the R parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1 fb(-1) collected by the Collider Detector at Fermilab experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence …

Further search for supersymmetry ats=7  TeVin final states with jets, missing transverse momentum, and isolated leptons with the ATLAS detector

This work presents a new inclusive search for supersymmetry (SUSY) by the ATLAS experiment at the LHC in proton-proton collisions at a center-of-mass energy root s = 7 TeV in final states with jets, missing transverse momentum and one or more isolated electrons and/or muons. The search is based on data from the full 2011 data-taking period, corresponding to an integrated luminosity of 4.7 fb(-1). Single-lepton and multilepton channels are treated together in one analysis. An increase in sensitivity is obtained by simultaneously fitting the number of events in statistically independent signal regions, and the shapes of distributions within those regions. A dedicated signal region is introduc…

Search for a Light Higgs Boson Decaying to Long-Lived Weakly Interacting Particles in Proton-Proton Collisions ats=7  TeVwith the ATLAS Detector

A search for the decay of a light Higgs boson (120-140 GeV) to a pair of weakly interacting, long-lived particles in 1.94 fb(-1) of proton-proton collisions at root s = 7 TeV recorded in 2011 by the ATLAS detector is presented. The search strategy requires that both long-lived particles decay inside the muon spectrometer. No excess of events is observed above the expected background and limits on the Higgs boson production times branching ratio to weakly interacting, long-lived particles are derived as a function of the particle proper decay length.

Production ofΛ0,Λ¯0,Ξ±, andΩ±hyperons inpp¯collisions ats=1.96  TeV

We report a set of measurements of inclusive invariant ${p}_{T}$ differential cross sections of ${\ensuremath{\Lambda}}^{0}$, ${\overline{\ensuremath{\Lambda}}}^{0}$, ${\ensuremath{\Xi}}^{\ifmmode\pm\else\textpm\fi{}}$, and ${\ensuremath{\Omega}}^{\ifmmode\pm\else\textpm\fi{}}$ hyperons reconstructed in the central region with pseudorapidity $|\ensuremath{\eta}|l1$ and ${p}_{T}$ up to $10\text{ }\text{ }\mathrm{GeV}/c$. Events are collected with a minimum-bias trigger in $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV using the CDF II detector at the Tevatron Collider. As ${p}_{T}$ increases, the slopes of the differential cross sections of the three particles are similar,…

Search for extra dimensions in diphoton events from proton-proton collisions at root s=7 TeV in the ATLAS detector at the LHC

The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton–proton collisions at √s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9fb[superscript −1]. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali, 95% confidence le…

Measurement of theCP-violating phaseβsJ/ψϕinBs0→J/ψϕdecays with the CDF II detector

We present a measurement of the \CP-violating parameter \betas using approximately 6500 $$\BsJpsiPhi$$ decays reconstructed with the CDF\,II detector in a sample of $$p\bar p$$ collisions at $$\sqrt{s}=1.96$$ TeV corresponding to 5.2 fb$$^{-1}$$ integrated luminosity produced by the Tevatron Collider at Fermilab. We find the \CP-violating phase to be within the range $$\betas \in [0.02, 0.52] \cup [1.08, 1.55]$$ at 68% confidence level where the coverage property of the quoted interval is guaranteed using a frequentist statistical analysis. This result is in agreement with the standard model expectation at the level of about one Gaussian standard deviation. We consider the inclusion of a po…

Direct Top-Quark Width Measurement at CDF

7 páginas, 2 figuras, 2 tablas.-- CDF Collaboration: et al.

Searches for supersymmetry with the ATLAS detector using final states with two leptons and missing transverse momentum in s=7 TeV proton–proton collisions

Results of three searches are presented for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons, e or mu. The analysis uses a data sample collected during the first half of 2011 that corresponds to a total integrated luminosity of 1 fb(-1) of root s = 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. Opposite-sign and same-sign dilepton events are separately studied, with no deviations from the Standard Model expectation observed. Additionally, in opposite-sign events, a search is made for an excess of same-flavour over different-flavour lepton pairs. Effective pro…

Search for Production of Resonant States in the Photon-Jet Mass Distribution UsingppCollisions ats=7  TeVCollected by the ATLAS Detector

This Letter describes a model-independent search for the production of new resonant states in photon + jet events in 2.11 fb(-1) of proton-proton collisions at root s = 7 TeV. We compare the photon ...

Combination of CDF and D0 W-Boson mass measurements

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…

Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector ins=7  TeVppCollisions

This Letter presents the first search for supersymmetry in final states containing one isolated electron or muon, jets, and missing transverse momentum from sqrt{s} = 7 TeV proton-proton collisions at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of 35 pb-1. No excess above the standard model background expectation is observed. Limits are set on the parameters of the minimal supergravity framework, extending previous limits. For A_0 = 0 GeV, tan beta = 3, mu > 0 and for equal squark and gluino masses, gluino masses below 700 GeV are excluded at 95% confidence level.

Search for Large Extra Dimensions in Final States Containing One Photon or Jet and Large Missing Transverse Energy Produced inpp¯Collisions ats=1.96  TeV

We present the results of searches for large extra dimensions in samples of events with large missing transverse energy E_{T} and either a photon or a jet produced in pp[over ] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II. For gamma+E_{T} and jet+E_{T} candidate samples corresponding to 2.0 and 1.1 fb;{-1} of integrated luminosity, respectively, we observe good agreement with standard model expectations and obtain a combined lower limit on the fundamental parameter of the large extra dimensions model M_{D} as a function of the number of extra dimensions in the model.

Search for the DecaysB(s)0→e+μ−andB(s)0→e+e−in CDF Run II

We report results from a search for the lepton flavor violating decays $B^0_{(s)}\to e^+\mu^-$, and the flavor-changing neutral-current decays $B^0_{(s)} \to e^+ e^-$. The analysis uses data corresponding to ${\rm 2 fb^{-1}}$ of integrated luminosity of $p \bar{p}$ collisions at $\sqrt{s}=1.96 {\rm TeV}$ collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron. The observed number of $B^0_{(s)}$ candidates is consistent with background expectations. The resulting Bayesian upper limits on the branching ratios at 90% credibility level are $\mathcal{B}(B^0_s \to e^{+}\mu^{-}) 47.8 {\rm TeV/c^2}$, and ${M_{LQ}}(B^0\to e^+ \mu^-) > 59.3 {\rm TeV/c^2}$, at 90% credibility l…

Search for a Higgs Boson Decaying to Two W Bosons at CDF

We present a search for a Higgs boson decaying to two W bosons in p (p) over bar collisions at root s = 1.96 TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200 GeV/c(2), and determine upper limits on the production cross section. For the mass of 160 GeV/c(2), where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section.

Observation of Spin Correlation intt¯Events fromppCollisions ats=7  TeVUsing the ATLAS Detector

A measurement of spin correlation in t (t) over bar production is reported using data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 2.1 fb(-1). Candidat ...

Measurement ofW+W−production inppcollisions ats=7  TeVwith the ATLAS detector and limits on anomalousWWZandWWγcouplings

This paper presents a measurement of the W+W- production cross section in pp collisions at root s = 7 TeV. The leptonic decay channels are analyzed using data corresponding to an integrated luminosity of 4: 6 fb(-1) collected with the ATLAS detector at the Large Hadron Collider. The W+W- production cross section sigma(pp -> W+W- + X) is measured to be 51.9 +/- 2.0(stat) +/- 3.9(syst) +/- 2.0(lumi) pb, compatible with the Standard Model prediction of 44.7(-1.9)(+2.1) pb. A measurement of the normalized fiducial cross section as a function of the leading lepton transverse momentum is also presented. The reconstructed transverse momentum distribution of the leading lepton is used to extract li…

Search for heavy vector-like quarks coupling to light quarks in proton–proton collisions at s=7 TeV with the ATLAS detector

This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value…

Search for contact interactions in dimuon events fromppcollisions ats=7  TeVwith the ATLAS detector

A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at root s = 7 TeV. The data sample corresponds to an integrated ...

Measurement of the top quark mass in the dilepton channel using mT2 at CDF

We present measurements of the top quark mass using mT2, a variable related to the transverse mass in events with two missing particles. We use the template method applied to tt̅ dilepton events produced in pp̅ collisions at Fermilab’s Tevatron Collider and collected by the CDF detector. From a data sample corresponding to an integrated luminosity of 3.4  fb-1, we select 236 tt̅ candidate events. Using the mT2 distribution, we measure the top quark mass to be Mtop=168.0-4.0+4.8(stat)±2.9(syst)  GeV/c2. By combining mT2 with the reconstructed top quark mass distributions based on a neutrino weighting method, we measure Mtop=169.3±2.7(stat)±3.2(syst)  GeV/c2. This is the first application of …

Combination of the top-quark mass measurements from the Tevatron collider

Aaltonen, T. et al.

Measurement of the W±Z production cross section and limits on anomalous triple gauge couplings in proton–proton collisions at s=7 TeV with the ATLAS detector

This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected w ...

Combined performance studies for electrons at the 2004 ATLAS combined test-beam

In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Ra…

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb

et al.

Inclusive Search for Squark and Gluino Production inpp¯Collisions ats=1.96  TeV

We report on a search for inclusive production of squarks and gluinos in p{bar p} collisions at {radical}s = 1.96 TeV, in events with large missing transverse energy and multiple jets of hadrons in the final state. The study uses a CDF Run II data sample corresponding to 2 fb-1 of integrated luminosity. The data are in good agreement with the standard model predictions, giving no evidence for any squark or gluino component. In an R-parity conserving minimal supergravity scenario with A{sub 0} = 0, mu < 0 and tan beta = 5, 95% C.L. upper limits on the production cross sections in the range between 0.1 pb and 1 pb are obtained, depending on the squark and gluino masses considered. For gluino …

Search for neutral MSSM Higgs bosons decaying to τ+τ− pairs in proton–proton collisions at s=7 TeV with the ATLAS detector

A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb^-1. After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson mass and for A/H/h production in the Minimal Supersymmetric Standard Model (MSSM) as a function of…

Top quark mass measurement in the lepton plus jets channel using a modified matrix element method

We report a measurement of the top quark mass, m(t), obtained from p(p)over bar collisions at root s=1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb(-1). We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of m(t) and a parame…

Measurement of the inclusive isolated prompt photon cross section inppcollisions ats=7  TeVwith the ATLAS detector

A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E-T(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed d…

Search for displaced muonic lepton jets from light Higgs boson decay in proton–proton collisions at s=7 TeV with the ATLAS detector

A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at root s = 7 TeV centre-of-mass ...

Measurements of branching fraction ratios andCPasymmetries inB±→DCPK±decays in hadron collisions

9 paginas, 3 figuras, 2 tablas.-- PACS numbers: 13.25.Hw, 11.30.Er, 14.40.Nd.--CDF Collaboration: et al.

Search for excited leptons in proton-proton collisions ats=7  TeVwith the ATLAS detector

The ATLAS detector is used to search for excited leptons in the electromagnetic radiative decay channel l* -> l gamma. Results are presented based on the analysis of pp collisions at a center-of ...

Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs.

et al.

Measurement of the b-hadron production cross section using decays to D⁎+μ−X final states in pp collisions at s=7 TeV with the ATLAS detector

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at root s = 7 TeV, using 3.3 pb(-1) of integrated luminosity, collected during the 2010 LHC run. The b-had ...

Search for the Production of Scalar Bottom Quarks inpp¯Collisions ats=1.96  TeV

We report on a search for direct scalar bottom quark (sbottom) pair production in pp collisions at {radical}(s)=1.96 TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a b quark. The study uses a collider detector at Fermilab Run II data sample corresponding to 2.65 fb{sup -1} of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits on the sbottom pair production cross se…

Search for Magnetic Monopoles ins=7  TeVppCollisions with the ATLAS Detector

This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb(-1) of pp collisions recorded at a center-of- ...

Underlying event characteristics and their dependence on jet size of charged-particle jet events inppcollisions at(s)=7  TeVwith the ATLAS detector

Distributions sensitive to the underlying event are studied in events containing one or more charged-particle jets produced in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). These measurements reflect 800 inverse microbarns of data taken during 2010. Jets are reconstructed using the antikt algorithm with radius parameter R varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle pT are measured as functions of pT^JET in regions transverse to and opposite the leading jet for 4 GeV < pT^JET < 100 GeV. In addition, the R-dependen…

Measurement ofW-Boson Polarization in Top-Quark Decay inpp¯Collisions ats=1.96  TeV

We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb(-1) of p (p) over bar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c(2), three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f(0)) and right-handed (f(0)) W bosons yields the model- independent results f(0) =0. 88 +/- 0.11(stat) +/- 0.06(syst) and f(+) = 0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient of -0.59. A measurement of f(0) [f(+)] constraining f(+) [f(0)] to its standard model value of 0.0 [0.7] yields f(0) 0.70 + 0.07(stat) +/- 0.04(syst) [f(+) - 0.01 +/- 0.02(stat) +/- 0.05(syst)]. All these resu…

Measurement of the ϒ(1S) production cross-section in pp collisions at s=7 TeV in ATLAS

A measurement of the cross-section for ϒ ( 1 S ) → μ + μ − production in proton–proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ ( 1 S ) transverse momentum in two bins of rapidity, | y ϒ ( 1 S ) | 4 GeV and pseudorapidity | η μ | < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb−1, collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model incl…

Search for the neutral current top quark decayt→Zcusing the ratio ofZ-boson+4  jetstoW-boson+4  jetsproduction

We have used the Collider Detector at Fermilab (CDF II) to search for the flavor-changing neutral-current (FCNC) top quark decay t {yields} Zc using a technique employing ratios of W and Z production, measured in p{bar p} data corresponding to an integrated luminosity of 1.52 fb{sup -1}. The analysis uses a comparison of two decay chains, p{bar p} {yields} t{bar t} {yields} WbWb {yields} {ell}{nu}bjjb and p{bar p} {yields} t{bar t} {yields} ZcWb {yields} {ell}{ell}cjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multi-year dataset using another ratio of W and Z product…

Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of theW→ℓνandZ→ℓℓCross Sections

AQCD analysis is reported of ATLAS data on inclusive W-+/- and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x similar to 0:01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1:00(-0:28)(+0.25) at absolute four-momentum transfer squared Q(2) = 1: 9 GeV2 and x = 0: 023.

Search for Supersymmetry in Events with Three Leptons and Missing Transverse Momentum ins=7  TeVppCollisions with the ATLAS Detector

A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses 2.06 fb(-1) of root s = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to …

Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at s=7 TeV

The results of a search for pair production of the lighter scalar partners of top quarks () in 2.05 fb−1 of pp collisions at TeV using the ATLAS experiment at the LHC are reported. Scalar top quar ...

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using4.7  fb−1ofs=7  TeVproton-proton collision data

A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-p(T) electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb(-1). No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino, for squark or gluino masses below 2 TeV, respectively. Squarks and glui…

Search for a Supersymmetric Partner to the Top Quark in Final States with Jets and Missing Transverse Momentum ats=7  TeVwith the ATLAS Detector

A search for direct pair production of supersymmetric top squarks ((t) over tilde (1)) is presented, assuming the (t) over tilde (1) decays into a top quark and the lightest supersymmetric particle, (chi) over tilde (0)(1), and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5(-3.6)(+3.7) (4.4(-1.3)(+1.7)) events in two signal regions based on integral Ldt = 4.7 fb(-1) of pp collision data taken at root s = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the (t) over tilde (1) versus (chi) over tilde (0)(1) mass plane is evaluated: 370 1) 10) similar to 0 GeV while m((t…

Observation of a NewχbState in Radiative Transitions toΥ(1S)andΥ(2S)at ATLAS

The χb(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at √s=7  TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4  fb-1, these states are reconstructed through their radiative decays to Υ(1S,2S) with Υ→μ+μ-. In addition to the mass peaks corresponding to the decay modes χb(1P,2P)→Υ(1S)γ, a new structure centered at a mass of 10.530±0.005(stat)±0.009(syst)  GeV is also observed, in both the Υ(1S)γ and Υ(2S)γ decay modes. This structure is interpreted as the χb(3P) system.

Measurement of the single-top-quark production cross section at CDF.

We report a measurement of the single top quark production cross section in 2.2 ~fb-1 of p-pbar collision data collected by the Collider Detector at Fermilab at sqrt{s}=1.96 TeV. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2 +0.7 -0.6(stat+sys) pb, extract the CKM matrix element value |V_{tb}|=0…

Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in s=7 TeV proton–proton collisions

A search is presented for a narrow resonance decaying to a pair of Z bosons using data corresponding to 1.02 fb(-1) of integrated luminosity collected by the ATLAS experiment from pp collisions at ...

Measurement ofD*±meson production in jets fromppcollisions ats=7  TeVwith the ATLAS detector

This paper reports a measurement of D*(+/-) meson production in jets from proton- proton collisions at a center- of- mass energy of root s = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb(-1) for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range vertical bar eta vertical bar D-0 pi(+), D-0 -> K-pi(+), and its charge conjugate. The production rate is found to be N(D*(+/-))/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*(+/-) mesons that carry a fraction z of the jet momentum in the range 0.3< z< 1. Monte Carlo predictions fail to describe the dat…

Search for high-mass resonances decaying to dilepton final states in pp collisions at √s = 7 TeV with the ATLAS detector

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z′ gauge bosons, Randall-Sundrum gravitons, Z [superscript *] bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb[superscript −1] in the e [superscript +] e [superscript −] channel and 5.0 fb[superscript −1] in the μ [superscript +] μ [superscript −] channel. A Z [superscript ′] boson with Standard Model-like couplings…

Measurement of the Ratioσtt¯/σZ/γ*→lland Precise Extraction of thett¯Cross Section

We report a measurement of the ratio of the t (t) over bar to Z/gamma* production cross sections in root s = 1.96 TeV p (p) over bar collisions using data corresponding to an integrated luminosity of up to 4.6 fb(-1), collected by the CDF II detector. The t (t) over bar cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/gamma* -> ll cross section predicted by the standard model, the extracted t (t) over bar cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the resul…

Search for Supersymmetry inppCollisions ats=7  TeVin Events with Two Photons and Missing Transverse Energy

A search for supersymmetry in the context of general gauge-mediated breaking with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest is presented. The data sample corresponds to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment at the LHC. The search is performed by using events containing two or more isolated photons, at least one hadronic jet, and significant missing transverse energy. No excess of events at high missing transverse energy is observed. Upper limits on the signal cross section for general gauge-mediated supersymmetry between 0.3 and 1.1 pb at the 95% confidence level are determined for a range of squa…

Measurement of the top quark mass andpp¯→tt¯cross section in the all-hadronic mode with the CDF II detector

We present a measurement of the top quark mass and of the top-antitop pair production cross section using p-pbar data collected with the CDFII detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9 fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the abs…

Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions atsNN=2.76  TeVwith the ATLAS Detector at the LHC

By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymme…

Measurement of the top pair production cross section in the dilepton decay channel inpp¯collisions ats=1.96  TeV

A measurement of the tt production cross section in pp collisions at {radical}(s)=1.96 TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II detector. The result in a data sample corresponding to an integrated luminosity 2.8 fb{sup -1} is {sigma}{sub tt}=6.27{+-}0.73(stat){+-}0.63(syst){+-}0.39(lum) pb. for an assumed top mass of 175 GeV/c{sup 2}.

Study of jet shapes in inclusive jet production inppcollisions ats=7  TeVusing the ATLAS detector

Jet shapes have been measured in inclusive jet production in proton-proton collisions at root s = 7 TeV using 3 pb(-1) of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-k(t) algorithm with transverse momentum 30 GeV < p(T) < 600 GeV and rapidity in the region vertical bar y vertical bar < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the je…

Search for Scalar Bottom Quark Pair Production with the ATLAS Detector inppCollisions ats=7  TeV

The results of a search for pair production of the scalar partners of bottom quarks in 2: 05 fb(-1) of pp collisions at root s = 7 TeV using the ATLAS experiment are reported. Scalar bottom quarks ...

Measurement of inclusive jet and dijet production inppcollisions ats=7  TeVusing the ATLAS detector

Inclusive jet and dijet cross sections have been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The cross sections were measured using jets clustered with the anti-kT algorithm with parameters R=0.4 and R=0.6. These measurements are based on the 2010 data sample, consisting of a total integrated luminosity of 37 inverse picobarns. Inclusive jet double-differential cross sections are presented as a function of jet transverse momentum, in bins of jet rapidity. Dijet double-differential cross sections are studied as a function of the dijet invariant mass, in bins of half the rapidity separation of the two leading …

Search for ExclusiveZ-Boson Production and Observation of High-Masspp¯→pγγp¯→pl+l−p¯Events inpp¯Collisions ats=1.96  TeV

We present a search for exclusive Z boson production in proton-antiproton collisions at {radical}s = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z {yields} {ell}{sup +}{ell}{sup -} candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, {sigma}{sub excl}(Z) 40 GeV=c{sup 2} and |{eta}{sub {ell}}| < 4 to be {sigma} = 0.24{sub -0.10}{sup +0.13} pb, which is the first measurement for this mass range and is consistent with the standard model prediction.

Inclusive search for same-sign dilepton signatures in pp collisions at $ sqrt {s} = 7 $ TeV with the ATLAS detector

An inclusive search is presented for new physics in events with two isolated leptons (e or mu) having the same electric charge. The data are selected from events collected from p p collisions at root s = 7 TeV by the ATLAS detector and correspond to an integrated luminosity of 34 pb(-1). The spectra in dilepton invariant mass, missing transverse momentum and jet multiplicity are presented and compared to Standard Model predictions. In this event sample, no evidence is found for contributions beyond those of the Standard Model. Limits are set on the cross-section in a fiducial region for new sources of same-sign high-mass dilepton events in the ee, e mu and mu mu channels. Four models predic…

Search for Pair Production of a Heavy Up-Type Quark Decaying to aWBoson and abQuark in thelepton+jetsChannel with the ATLAS Detector

A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming subsequent decay to a W boson and a b quark, t'(t) over bar' -> W(+)bW(-)(b) over bar. The search is based on 1.04 fb(-1) of proton-proton collisions at root s = 7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton + jets final state, characterized by a high transverse momentum isolated electron or muon, high missing transverse momentum, and at least three jets. No significant excess of events above the background expectation is observed. A 95% C.L. lower limit of 404 GeV is set for the mass of the t' quark.

Search for the Higgs Boson in theH→WW→lνjjDecay Channel inppCollisions ats=7  TeVwith the ATLAS Detector

A search for a Higgs boson has been performed in the H -> WW -> l nu jj channel in 1.04 fb(-1) of pp collision data at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 240 GeV WW production is 3.1 pb, or 2.7 times the standard model prediction.

Search for New Physics with a Dijet Plus MissingETSignature inpp¯Collisions ats=1.96  TeV

We present results of a signature-based search for new physics using a dijet plus missing transverse energy (E{sub T}) data sample collected in 2 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. We observe no significant event excess with respect to the standard model prediction and extract a 95% C.L. upper limit on the cross section times acceptance for a potential contribution from a non-standard model process. Based on this limit the mass of a potential first or second generation scalar leptoquark is constrained to be above 187 GeV/c{sup 2}.

Measurement ofb-jet shapes in inclusive jet production inpp¯collisions ats=1.96  TeV

We present a measurement of the shapes of b-jets using 300 pb(-1) of data obtained with the upgraded Collider Detector at Fermilab (CDF II) in p(p)overbar collisions at center-of-mass energy root s=1.96 TeV. This measurement covers a wide transverse momentum range, from 52 to 300 GeV/c. Samples of heavy-flavor enhanced jets together with inclusive jets are used to extract the average shapes of b-jets. The b-jets are expected to be broader than inclusive jets. Moreover, b-jets containing a single b-quark are expected to be narrower than those containing a b(b)overbar pair from gluon splitting. The measured b-jet shapes are found to be significantly broader than expected from the PYTHIA and H…

Ks0andΛproduction inppinteractions ats=0.9and 7 TeV measured with the ATLAS detector at the LHC

The production of K(S)(0) and Lambda hadrons is studied in pp collision data at root s = 0.9 and 7 TeV collected with the ATLAS detector at the LHC using a minimum-bias trigger. The observed distributions of transverse momentum, rapidity, and multiplicity are corrected to hadron level in a model-independent way within well-defined phase-space regions. The distribution of the production ratio of (Lambda) over bar to Lambda baryons is also measured. The results are compared with various Monte Carlo simulation models. Although most of these models agree with data to within 15% in the K(S)(0) distributions, substantial disagreements are found in the Lambda distributions of transverse momentum.

Search for the Standard Model Higgs boson in the decay channel H→ZZ(⁎)→4ℓ with 4.8 fb−1 of pp collision data at s=7 TeV with ATLAS

This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for …

Search for high mass dilepton resonances in pp collisions at s=7 TeV with the ATLAS experiment

This Letter presents a search for high mass e(+)e(-) or mu(+)mu(-) resonances in pp collisions at root s = 7 TeV at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspon ...

Measurement of pion and proton response and longitudinal shower profiles up to 20 nuclear interaction lengths with the ATLAS Tile calorimeter

The response of pions and protons in the energy range of 20–180 GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-indu…

Search for TeV-scale gravity signatures in final states with leptons and jets with the ATLAS detector at s=7 TeV

A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.

Search for Anomalous Production of Events with a Photon, Jet, b-quark Jet, and Missing Transverse Energy

We present a signature-based search for the anomalous production of events containing a photon, two jets, of which at least one is identified as originating from a b quark, and missing transverse energy ((sic)(T)). The search uses data corresponding to 2.0 fb(-1) of integrated luminosity from p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. From 6.697 47 x 10(6) events with a photon candidate with transverse energy E-T > 25 GeV, we find 617 events with (sic)(T) > 25 GeV and two or more jets with E-T > 15 GeV, at least one identified as originating from a b quark, versus an expectation of 607 +/- 113 event…

Top quark mass measurement in thett¯all hadronic channel using a matrix element technique inpp¯collisions ats=1.96  TeV

We present a measurement of the top quark mass in the all hadronic channel ($t\overline{t}\ensuremath{\rightarrow}b\overline{b}{q}_{1}{\overline{q}}_{2}{q}_{3}{\overline{q}}_{4}$) using $943\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ collected at the CDF II detector at Fermilab (CDF). We apply the standard model production and decay matrix element (ME) to $t\overline{t}$ candidate events. We calculate per-event probability densities according to the ME calculation and construct template models of signal and background. The scale of the jet energy is calibrated using additional templates formed with the invaria…

Search for New Bottomlike Quark Pair DecaysQQ¯→(tW∓)(t¯W±)in Same-Charge Dilepton Events

We report the most restrictive direct limits on masses of fourth-generation down-type quarks b{sup '}, and quarklike composite fermions (B or T{sub 5/3}), decaying promptly to tW{sup +}-. We search for a significant excess of events with two same-charge leptons (e, mu), several hadronic jets, and missing transverse energy. An analysis of data from pp collisions with an integrated luminosity of 2.7 fb{sup -1} collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits m{sub b}{sup '}, m{sub B}>338 GeV/c{sup 2} and m{sub T{sub 5{sub /{sub 3}}}}>365 GeV/c{sup 2} at 95% confidence level.

Search for Direct Top Squark Pair Production in Final States with One Isolated Lepton, Jets, and Missing Transverse Momentum ins=7  TeVppCollisions Using4.7  fb−1of ATLAS Data

A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at root s = 7 TeV. The measurement is based on 4.7 fb(-1) of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.

Search for pair-produced heavy quarks decaying toWqin the two-lepton channel at(s)=7  TeVwith the ATLAS detector

A search is presented for heavy-quark pair production (Q (Q) over bar) under the decay hypothesis Q (Q) over bar -> W(+)qW(-)(q) over bar with q = d, s, b for up-type Q or q = u, c for down-type ...

Search for the Standard Model Higgs Boson in the Diphoton Decay Channel with4.9  fb−1ofppCollision Data ats=7  TeVwith ATLAS

A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9  fb-1 collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of √s=7  TeV. In the diphoton mass range 110–150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110–150 GeV, this significance becomes 1.5 standard deviations. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges of 113–115 GeV and…

Searching the inclusiveℓγE̸T+b-quark signature for radiative top quark decay and non-standard-model processes

We compare the inclusive production of events containing a lepton (l), a photon ({gamma}), significant transverse momentum imbalance (Ee{sub T}), and a jet identified as containing a b-quark, to SM predictions. The search uses data produced in proton-antiproton collisions at {radical}(s)=1.96 TeV corresponding to 1.9 fb{sup -1} of integrated luminosity taken with the CDF detector. We find 28 l{gamma}bEe{sub T} events versus an expectation of 31.0{sub -3.5}{sup +4.1} events. If we further require events to contain at least three jets and large total transverse energy, the largest SM source is radiative top-quark pair production, tt+{gamma}. In the data we observe 16 tt{gamma} candidate event…

Search for high-mass resonances decaying to dimuons at CDF.

We present a search for high-mass neutral resonances using dimuon data corresponding to an integrated luminosity of 2.3 fb(-1) collected in pp collisions at s=1.96 TeV by the CDF II detector at the Fermilab Tevatron. No significant excess above the standard model expectation is observed in the dimuon invariant-mass spectrum. We set 95% confidence level upper limits on sigma BR(pp -> X ->mu mu), where X is a boson with spin-0, 1, or 2. Using these cross section limits, we determine lower mass limits on sneutrinos in R-parity-violating supersymmetric models, Z(') bosons, and Kaluza-Klein gravitons in the Randall-Sundrum model.

Measurement ofZγproduction inpp¯collisions ats=1.96  TeV

The production rate and kinematics of photons produced in association with Z bosons are studied using 2 fb{sup -1} of p{bar p} collision data collected at the Collider Detector at Fermilab. The cross section for p{bar p} {yields} {ell}{sup +}{ell}{sup -}{gamma} + X (where the leptons {ell} are either muons or electrons with dilepton mass M{sub {ell}{ell}} > 40 GeV/c{sup 2}, and where the photon has transverse energy E{sub T}{sup {gamma}} > 7 GeV and is well separated from the leptons) is 4.6 {+-} 0.2 (stat) {+-} 0.3 (syst) {+-} 0.3 (lum) pb, which is consistent with standard model expectations. We use the photon ET distribution from Z{gamma} events where the Z has decayed to {mu}{sup +}{mu}…

Measurement of the inclusiveW±andZ/γ*cross sections in theeandμdecay channels inppcollisions ats=7  TeVwith the ATLAS detector

The production cross sections of the inclusive Drell-Yan processes W-+/- -> l nu and Z/gamma* -> ll (l = e, mu) are measured in proton-proton collisions at root s = 7 TeV with the ATLAS detector. The cross sections are reported integrated over a fiducial kinematic range, extrapolated to the full range, and also evaluated differentially as a function of the W decay lepton pseudorapidity and the Z boson rapidity, respectively. Based on an integrated luminosity of about 35 pb(-1) collected in 2010, the precision of these measurements reaches a few percent. The integrated and the differential W-+/- and Z/gamma* cross sections in the e and mu channels are combined, and compared with perturbative…

Observation of the Baryonic Flavor-Changing Neutral Current Decay Λb0→Λμ+μ-

8 páginas, 2 figuras, 4 tablas.-- PACS numbers: 13.30.Ce, 12.15.Mm, 14.20.Mr.-- CDF Collaboration: et al.

Measurement of Dijet Azimuthal Decorrelations inppCollisions ats=7  TeV

Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set ( integral Ldt = 36 pb(-1)) acquired by the ATLAS detector during the 2010 root s = 7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime.

Measurement of the WW cross section in s=7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings

This Letter reports a measurement of the W W production cross section in root s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb(-1) collected with the ATLAS de ...

Mechanical construction and installation of the ATLAS tile calorimeter

This paper summarises the mechanical construction andinstallation of the Tile Calorimeter for the ATLASexperiment at the Large Hadron Collider in CERN, Switzerland. The TileCalorimeter is a sampling calorimeter using scintillator as the sensitivedetector and steel as the absorber and covers the central region of the ATLASexperiment up to pseudorapidities ±1.7. The mechanical construction ofthe Tile Calorimeter occurred over a periodof about 10 years beginning in 1995 with the completionof the Technical Design Report and ending in 2006 with the installationof the final module in the ATLAS cavern. Duringthis period approximately 2600 metric tons of steel were transformedinto a laminated struc…

Search for new particles decaying into dijets in proton-antiproton collisions at root s=1.96 TeV

We present a search for new particles which produce narrow two-jet (dijet) resonances using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb(-1) collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude vertical bar y vertical bar < 1. These limits are used to determine the mass exclusions for the excited quark, axig…

Search for Heavy, Long-Lived Neutralinos that Decay to Photons at CDF II Using Photon Timing

We present the results of the first hadron collider search for heavy, long-lived neutralinos that decay via lightest neutralino to gamma gravitino in gauge-mediated supersymmetry breaking models. Using an integrated luminosity of $570\pm34 pb^{-1}$ of $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV, we select $\gamma$+jet+missing transverse energy candidate events based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed on the CDF II detector. We find 2 events, consistent with the background estimate of 1.3$\pm$0.7 events. While our search strategy does not rely on model-specific dynamics, we set cross sec…

Search for the Higgs Boson Produced in Association withZ→ℓ+ℓ−inpp¯Collisions ats=1.96  TeV

We present a search for associated production of the standard model (SM) Higgs boson and a Z boson where the Z boson decays to two leptons and the Higgs decays to a pair of b quarks in p{bar p} collisions at the Fermilab Tevatron. We use event probabilities based on SM matrix elements to construct a likelihood function of the Higgs content of the data sample. In a CDF data sample corresponding to an integrated luminosity of 2.7 fb{sup -1} we see no evidence of a Higgs boson with a mass between 100 GeV/c{sup 2} and 150 GeV/c{sup 2}. We set 95% confidence level (C.L.) upper limits on the cross-section for ZH production as a function of the Higgs boson mass m{sub H}; the limit is 8.2 times the…

Search for supersymmetry with jets, missing transverse momentum and at least one hadronically decaying τ lepton in proton–proton collisions at s=7 TeV with the ATLAS detector

A search for production of supersymmetric particles in final states containing jets, missing transverse momentum, and at least one hadronically decaying tau lepton is presented. The data were recor ...

Measurement ofbHadron Lifetimes in Exclusive Decays Containing aJ/ψinpp¯Collisions ats=1.96  TeV

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B{sup +}{yields}J/{psi}K{sup +}, B{sup 0}{yields}J/{psi}K{sup *}(892){sup 0}, B{sup 0}{yields}J/{psi}K{sub s}{sup 0}, and {Lambda}{sub b}{sup 0}{yields}J/{psi}{Lambda}{sup 0} using data corresponding to an integrated luminosity of 4.3 fb{sup -1}, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are {tau}(B{sup +})=[1.639{+-}0.009(stat){+-}0.009(syst)] ps, {tau}(B{sup 0})=[1.507{+-}0.010(stat){+-}0.008(syst)] ps, and {tau}({Lambda}{sub b}{sup 0})=[1.537{+-}0.045(stat){+-}0.014(syst)] ps. The lifetime ratios are {tau}(B{sup +})/{tau}(B{sup 0})=[1.088{+-}0.009(stat){+-}0.004…

Measurement of underlying event characteristics using charged particles inppcollisions ats=900  GeVand 7 TeV with the ATLAS detector

Measurements of charged particle distributions, sensitive to the underlying event, have been performed with the ATLAS detector at the LHC. The measurements are based on data collected using a minimum-bias trigger to select proton-proton collisions at center-of-mass energies of 900 GeV and 7 TeV. The "underlying event" is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. Three regions are defined in azimuthal angle with respect to the highest transverse momentum charged particle in the event, such that the region transverse to the dominant momentum-flow is most sensitive to …

Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector ins=7  TeVppcollisions at the LHC

This Letter presents the first search for a heavy particle decaying into an e(+/-)mu(-/+) final state in root s = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except lambda(311)' = 0.11 and lambda(312) = 0.07. In a lepton flavor violating model, a Z'-like vector boson with masses of 0.70-1.0…

Search for contact interactions in dilepton events from pp collisions at s=7 TeV with the ATLAS detector

This Letter presents a search for contact interactions in the dielectron and dimuon channels using data from proton-proton collisions produced by the LHC at,root s = 7 TeV and recorded by the ATLAS ...

Search for Gluino-Mediated Bottom Squark Production inpp¯Collisions ats=1.96  TeV

We report on a search for the supersymmetric partner of the bottom quark produced from gluino decays in data from 2.5 fb{sup -1} of integrated luminosity collected by the Collider Detector at Fermilab at {radical}s = 1.96 TeV. Candidate events are selected requiring two or more jets and large missing transverse energy. At least two of the jets are required to be tagged as originating from a b quark to enhance the sensitivity. The results are in good agreement with the prediction of the standard model processes, giving no evidence for gluino decay to sbottom quarks. This result constrains the gluino-pair-production cross section to be less than 40 fb at 95% credibility level for a gluino mas…

Search for diphoton events with large missing transverse energy in 7 TeV proton-proton collisions with the ATLAS detector.

A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at √s=7  TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3.1  pb−1. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R<729  GeV are excluded at 95% C. L., providing the most sensitive limit on this model to date.

First simultaneous measurement of the top quark mass in thelepton+jetsand dilepton channels at CDF

We present a measurement of the mass of the top quark using data corresponding to an integrated luminosity of 1.9 fb{sup -1} of pp collisions collected at {radical}(s)=1.96 TeV with the CDF II detector at Fermilab's Tevatron. This is the first measurement of the top quark mass using top-antitop pair candidate events in the lepton+jets and dilepton decay channels simultaneously. We reconstruct two observables in each channel and use a nonparametric kernel density estimation technique to derive two-dimensional probability density functions from simulated signal and background samples. The observables are the top quark mass and the invariant mass of two jets from the W decay in the lepton+jets…

First Observation of Vector Boson Pairs in a Hadronic Final State at the Tevatron Collider

We present the first observation in hadronic collisions of the electroweak production of vector boson pairs (VV, V=W, Z) where one boson decays to a dijet final state. The data correspond to 3.5 fb(-1) of integrated luminosity of pp collisions at s=1.96 TeV collected by the CDF II detector at the Fermilab Tevatron. We observe 1516 +/- 239(stat)+/- 144(syst) diboson candidate events and measure a cross section sigma(pp -> VV+X) of 18.0 +/- 2.8(stat)+/- 2.4(syst)+/- 1.1(lumi) pb, in agreement with the expectations of the standard model.