Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector in s=7TeV pp Collisions (original) (raw)
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2012
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 Modellike couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in data, and upper limits on the cross section times the branching ratio of W ′ R resonances at 95% CL lie in the range 6.1-1.0 pb for W ′ R masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed W ′ R mass, giving m W ′ R > 1.13 TeV at 95% CL.
The European Physical Journal C, 2012
A measurement of the jet activity in tt events produced in proton-proton collisions at a centre-ofmass energy of 7 TeV is presented, using 2.05 fb −1 of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. The tt events are selected in the dilepton decay channel with two identified b-jets from the top quark decays. Events are vetoed if they contain an additional jet with transverse momentum above a threshold in a central rapidity interval. The fraction of events surviving the jet veto is presented as a function of this threshold for four different central rapidity interval definitions. An alternate measurement is also performed, in which events are vetoed if the scalar transverse momentum sum of the additional jets in each rapidity interval is above a threshold. In both measurements, the data are corrected for detector effects and compared to the theoretical models implemented in MC@NLO, Powheg, Alpgen and Sherpa. The experimental uncertainties are often smaller than the spread of theoretical predictions, allowing deviations between data and theory to be observed in some regions of phase space.
2012
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 collected from pp collisions at √ s = 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. Using events with a b-tagged jet and a Z boson reconstructed from opposite-charge electrons, the mass distribution of large transverse momentum b ′ candidates is tested for an enhancement. No evidence for a b ′ signal is detected in the observed mass distribution, resulting in the exclusion at 95% confidence level of b ′ quarks with masses m b ′ < 400 GeV that decay entirely via b ′ → Z + b. In the case of a vector-like singlet b ′ mixing solely with the third Standard Model generation, masses m b ′ < 358 GeV are excluded. (c)