Measurements of the $ \mathrm{t}\overline{\mathrm{t}} $ charge asymmetry using the dilepton decay channel in pp collisions at $ \sqrt{s} $ = 7 TeV

Abstract

The tt charge asymmetry in proton-proton collisions at √ s = 7 TeV is measured using the dilepton decay channel (ee, eµ, or µµ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0.010 ± 0.017 (stat) ± 0.008 (syst) and A lep C = 0.009 ± 0.010 (stat) ± 0.006 (syst). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt system. All measurements are consistent with the expectations of the standard model.

Inclusive and differential measurements of the tt¯ charge asymmetry in pp collisions at sKhachatryan1, Sirunyan2, Tumasyan3 et al. 2016Physics Letters BSelf Cite406210View full textAdd to dashboardCite

“…Theoretical predictions for this observable are of order 1% in the SM [10,11], but its sensitivity to new physics makes measurements of the effect interesting even when the precision is not high enough to establish the existence of the SM charge asymmetry. Both the CMS and ATLAS collaborations have published results based on the data collected at a centreof-mass energy √ s = 7 TeV, which are in agreement with the SM predictions [12][13][14][15].…”

Properties of the Top Quark

“…CMS has also recently published an asymmetry measurement using leptons (85), in agreement with the SM prediction.…”

“…Recent calculations at NLO, including electroweak corrections, predicted A C = 1.23 ± 0.05% at the LHC ( √ s = 7 TeV for pp collisions)(59). ATLAS and CMS measurements of the charge asymmetry (at √ s = 7 utilizing 5 fb −1 of data) have not observed any significant deviation from the SM(Figure 4(75,76,77,78,79)). ATLAS and CMS have also performed differential measurements as a function of m tt , rapidity, and transverse momentum, and have not observed deviations from the SM.…”

Top-Quark Physics at the LHC

“…In a further study using the full 7 TeV data set, the CMS collaboration measured the charge asymmetry in a sample of dileptonically decaying tt pairs [109]. In addition to the observable A C , a "lepton charge asymmetry" is defined as…”