Abstract
Differential and double-differential cross sections for the production of top quark pairs in proton-proton collisions at 13 TeV are measured as a function of jet multiplicity and of kinematic variables of the top quarks and the top quark-antiquark system. This analysis is based on data collected by the CMS experiment at the LHC corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurements are performed in the lepton+jets decay channels with a single muon or electron in the final state. The differential cross sections are presented at particle level, within a phase space close to the experimental acceptance, and at parton level in the full phase space. The results are compared to several standard model predictions.
Highlights
Studying the differential production cross sections of top quark pairs at high energies is a crucial ingredient in testing the standard model and searching for sources of new physics, which could alter the production rate
The Monte Carlo programs POWHEG [9,10,11,12] (v2) and MADGRAPH5_aMC@next-to-leading order (NLO) [13] (v2.2.2) (MG5_aMC@NLO) are used to simulate tt events. They include NLO quantum chromodynamics (QCD) matrix element calculations that are combined with the parton shower simulation of PYTHIA [14,15] (v8.205) (PYTHIA8) using the tune CUETP8M1 [16]
This value is calculated with next-to-NLO (NNLO) precision including the resummation of next-to-next-to-leading-logarithmic (NNLL) soft gluon terms
Summary
Studying the differential production cross sections of top quark pairs (tt) at high energies is a crucial ingredient in testing the standard model and searching for sources of new physics, which could alter the production rate. A measurement of the tt differential and doubledifferential production cross sections as a function of jet multiplicity and of kinematic variables of the top quarks and the tt system is presented. The differential cross sections are presented as a function of the transverse momentum pT and the absolute rapidity jyj of the hadronically (th) and the leptonically (tl) decaying top quarks, as a function of pT, jyj, and mass M of the tt system. For the particle-level measurement a proxy of the top quark is defined based on experimentally accessible quantities like jets, which consist of quasistable particles with a mean lifetime greater than 30 ps These are described by theoretical calculations that, in contrast to pure matrixelement calculations, involve parton shower and hadronization models.
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