Inclusive and differential measurements of the tt¯ charge asymmetry in pp collisions at s

Abstract

Inclusive and differential measurements of the tt charge asymmetry in pp collisions at √ s = 8 TeVThe CMS Collaboration * AbstractThe tt charge asymmetry is measured in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 fb −1 . Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010 ± 0.0068 (stat) ± 0.0037 (syst). In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the tt system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of −0.0035 ± 0.0072 (stat) ± 0.0031 (syst). All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model.

Measurement of the forward-backward asymmetry in low-mass bottom-quark pairs produced in proton-antiproton collisions

“…Additional measurements performed by D0 [10] and CDF [11] are in good agreement with the higher-order calculations. Similarly good agreement with the SM prediction is reported by the LHC experiments for the charge asymmetry in tt production [12][13][14][15][16].…”

A set of top quark spin correlation and polarization observables for the LHC: Standard Model predictions and new physics contributions

“…These operators induce contributions to the differential cross section that are odd under interchange of the t andt momenta while those of the initial (anti)quark are kept fixed. Using the recent CMS measurement [88] with their 8 TeV data, A C = 0.001 ± 0.008, and putting the couplingĉ 2 to zero, we obtain the 95 % C.L. bound −0.06 ≤ĉ AA ≤ 0.01; cf.…”

Top-quark physics at the Large Hadron Collider

“…Figure 30 illustrates the measurements of the charge asymmetry at 7 TeV in the single-lepton channel. Measurements of the inclusive and differential charge asymmetry were also performed at 8 TeV with very similar techniques [161,163]. The inclusive tt production charge asymmetry has been measured with uncertainties of 0.5 − 0.8%, dominated by statistical uncertainties.…”