Abstract
A measurement of the top quark pair production (mathrm{t}overline{mathrm{t}} ) cross section in proton–proton collisions at the centre-of-mass energy of 8,text {TeV} is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6,text {fb}^{-text {1}}. This analysis is performed in the mathrm{t}overline{mathrm{t}} decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured mathrm{t}overline{mathrm{t}} cross section is 228.5 pm 3.8,text {(stat)} pm 13.7,text {(syst)} pm 6.0,text {(lumi)} text { pb} . This measurement is compared with an analysis of 7,text {TeV} data, corresponding to an integrated luminosity of 5.0,text {fb}^{-text {1}}, to determine the ratio of 8,text {TeV} to 7,text {TeV} cross sections, which is found to be 1.43 pm 0.04,text {(stat)} pm 0.07,text {(syst)} pm 0.05,text {(lumi)} . The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.
Highlights
Top quarks are abundantly produced at the CERN LHC
A precise measurement of σtt is an important test of perturbative quantum chromodynamics (QCD) at high energies
The technique for extracting the tt cross section consists of a binned log-likelihood fit of signal and background to the distribution of a discriminant variable in data showing a good separation between signal and background: the invariant mass of the b jet related to the leptonic top quark and the lepton (M b)
Summary
The predicted top quark pair production cross section (σtt) in proton–proton (pp) collisions, at a centre-of-mass energy of. Precision tt cross section measurements can be used to constrain the top quark mass mt and QCD parameters, such as the strong coupling constant αS [1], or the parton distribution functions (PDF) of the proton [2]. To measure the ccaronscsels,etchteio2n01ra1tidoa, twa hseetreats√evser=al systematic uncertainties 7 TeV, corresponding to an integrated luminosity of 5.0 fb−1, has been concurrently analyzed with a similar strategy to the one developed for the cross section measurement at 8 TeV. The technique for extracting the tt cross section consists of a binned log-likelihood fit of signal and background to the distribution of a discriminant variable in data showing a good separation between signal and background: the invariant mass of the b jet related to the leptonic top quark and the lepton (M b).
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