Search for same-sign top-quark production and fourth-generation down-type quarks in pp collisions at √s = 7 TeV with the ATLAS detector
Journal of High Energy Physics 2012:4 (2012)
Abstract:
A search is presented for same-sign top-quark production and down-type heavy quarks of charge -1/3 in events with two isolated leptons (e or μ) that have the same electric charge, at least two jets and large missing transverse momentum. The data are selected from pp collisions at ps = 7 TeV recorded by the ATLAS detector and correspond to an integrated luminosity of 1.04 fb-1. The observed data are consistent with expectations from Standard Model processes. Upper limits are set at 95% confidence level on the cross section of new sources of same-sign top-quark pair production of 1.4-2.0 pb depending on the assumed mediator mass. Upper limits are also set on the pair-production cross-section for new heavy down-type quarks; a lower limit of 450 GeV is set at 95% confidence level on the mass of heavy down-type quarks under the assumption that they decay 100% of the time to Wt. Copyright CERN.Measurements of the angular distributions of muons from Υ decays in pp collisions at sqrt[s] = 1.96 TeV.
Physical review letters 108:15 (2012) 151802
Abstract:
The angular distributions of muons from Υ(1S,2S,3S) → μ+ μ- decays are measured using data from pp collisions at sqrt[s] = 1.96 TeV corresponding to an integrated luminosity of 6.7 fb(-1) and collected with the CDF II detector at the Fermilab Tevatron. This analysis is the first to report the full angular distributions as functions of transverse momentum p(T) for Υ mesons in both the Collins-Soper and s-channel helicity frames. This is also the first measurement of the spin alignment of Υ(3S) mesons. Within the kinematic range of Υ rapidity |y|<0.6 and p(T) up to 40 GeV/c, the angular distributions are found to be nearly isotropic.Search for the Standard Model Higgs Boson Produced in Association with a $Z$ Boson in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV
(2012)
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
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 709:4-5 (2012) 341-357
Abstract:
This Letter presents a measurement of W ±Z production in 1.02 fb -1 of pp collision data at s=7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1±1.4(stat.)-2.0+4.1(syst.) events. The total cross section for W ±Z production for Z/γ * masses within the range 66 GeV to 116 GeV is determined to be σWZtot=20.5-2.8+3.1(stat.)-1.3+1.4(syst.)-0.8+0.9(lumi.) pb, which is consistent with the Standard Model expectation of 17.30.8+1.3 pb. Limits on anomalous triple gauge boson couplings are extracted. © 2012 CERN.Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 709:4-5 (2012) 322-340