51ÁÔÆæÈë¿Ú

Abstract:

A search for a charged Higgs boson (H⁺) in tt decays is presented, where one of the top quarks decays via t →H ⁺ b, followed by H ⁺ → two jets (cs). The other top quark decays to Wb, where the W boson then decays into a lepton (e/μ) and a neutrino. The data were recorded in pp collisions at √ s = 7 TeV by the ATLAS detector at the LHC in 2011, and correspond to an integrated luminosity of 4.7 fb^−1. With no observation of a signal, 95 % confidence level (CL) upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons varying between 5 % and 1 % for H ⁺ masses between 90 GeV and 150 GeV, assuming B(H ⁺→cs) = 100 %.

Abstract:

The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at √s=7 TeV. The analyses use a data sample with an integrated luminosity of 4.6 fb-1 collected by the ATLAS detector during the 2011 LHC data-taking period. Events are selected using leptonic decays of the W and Z bosons [W(eν,μν) and Z(e+e-, μ+μ-,νν̄)] with the requirement of an associated isolated photon. The data are used to test the electroweak sector of the Standard Model and search for evidence for new phenomena. The measurements are used to probe the anomalous WWγ, ZZγ, and Zγγ triple-gauge-boson couplings and to search for the production of vector resonances decaying to Zγ and Wγ. No deviations from Standard Model predictions are observed and limits are placed on anomalous triple-gauge-boson couplings and on the production of new vector meson resonances. © 2013 CERN.

Abstract:

This paper reports a measurement of the W +b-jets (W +b+ X and W+b̄b+X) production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb-1, collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W +b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range. Combining the muon and electron channels, the fiducial cross-section for W +b-jets is measured to be 7.1 ± 0.5 (stat) ± 1.4 (syst) pb, consistent with the next-to-leading order QCD prediction, corrected for non-perturbative and double-parton interactions (DPI) contributions, of 4.70 ± 0.09 (stat)-0.49+0.60 (scale) ±0.06 (PDF) ±0.16 (non-pert)-0.38+0.52 (DPI) pb. © 2013 CERN for the benefit of the ATLAS collaboration.