1304.6386 (ATLAS collaboration)

A study of heavy flavor quarks produced in association with top quark
pairs at sqrt(s) = 7 TeV using the ATLAS detector    [PDF]

ATLAS collaboration

Using a sample of dilepton top-quark pair (ttbar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, ttbar + b + X or ttbar + c + X, collectively referred to as ttbar + HF. The dataset used corresponds to an integrated luminosity of 4.7 fb^-1 of proton--proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The dominant background to ttbar + HF in this sample is ttbar + jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result for extra HF production is quoted as a ratio (R_HF) of the cross section for ttbar + HF production to the cross section for ttbar production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. R_HF is measured to be [7.1 +/- 1.3 (stat.) +5.3/-2.0 (syst.)] % for jets with pt > 25 GeV and |eta| < 2.5, compared to the leading-order QCD Standard Model expectation of [3.4 +/- 1.1] %.

View original: http://arxiv.org/abs/1304.6386