Abstract
Differential and double-differential cross sections for the production of top quark pairs in proton-proton collisions at $\sqrt{s} =$ 13 TeV are measured as a function of kinematic variables of the top quarks and the top quark-antiquark ($\mathrm{t}\overline{\mathrm{t}}$) system. In addition, kinematic variables and multiplicities of jets associated with the $\mathrm{t}\overline{\mathrm{t}}$ production are measured. This analysis is based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.8 fb$^{-1}$. The measurements are performed in the lepton+jets decay channels with a single muon or electron and jets in the final state. The differential cross sections are presented at the particle level, within a phase space close to the experimental acceptance, and at the parton level in the full phase space. The results are compared to several standard model predictions that use different methods and approximations. The kinematic variables of the top quarks and the $\mathrm{t}\overline{\mathrm{t}}$ system are reasonably described in general, though none predict all the measured distributions. In particular, the transverse momentum distribution of the top quarks is more steeply falling than predicted. The kinematic distributions and multiplicities of jets are adequately modeled by certain combinations of next-to-leading-order calculations and parton shower models.
Highlights
Measurements of differential production cross sections of top quark pairs provide important information for testing the standard model and searching for phenomena beyond the standard model
Precise theoretical predictions of these measurements are challenging since higher-order effects of quantum chromodynamics (QCD) and electroweak (EW) corrections [1] are important
The generation of tt events requires a realistic modeling of the parton shower (PS)
Summary
Measurements of differential production cross sections of top quark pairs (tt) provide important information for testing the standard model and searching for phenomena beyond the standard model. The corrections and extrapolations used in this measurement are based on a next-to-leading-order (NLO) calculation of tt production, combined with a simulation of the PS For both particle- and parton-level measurements the tt system is reconstructed at the detector level with a likelihood-based approach using the top quark and W boson mass constraints to identify the corresponding top quark decay products. The differential cross sections are measured at the particle and parton levels as a function of the transverse momentum pT and the absolute rapidity jyj of the top quarks, separately for the hadronically (labeled th) and leptonically (labeled tl) decaying W bosons, and the pT, jyj, and invariant mass M of the tt system. The differential cross sections at the parton level are determined as a function of the lower- and higher-pT values of the top quarks in an event.
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