Inclusive and differential measurements of the $$ textrm{t}overline{textrm{t}}upgamma $$ cross section and the $$ textrm{t}overline{textrm{t}}upgamma /textrm{t}overline{textrm{t}} $$ cross section ratio in proton-proton collisions at $$ sqrt{s}=13 $$ TeV
Journal Article
Overview
abstract
; A; bstract; ; ; Inclusive and differential cross section measurements of top quark pair (; ; ; $$ textrm{t}overline{textrm{t}} $$; ; t; ; t; ¯; ; ; ; ; ) production in association with a photon (γ) are performed as a function of lepton, photon, top quark, and; ; ; $$ textrm{t}overline{textrm{t}} $$; ; t; ; t; ¯; ; ; ; ; kinematic observables, using data from proton-proton collisions at; ; ; $$ sqrt{s}=13 $$; ; ; s; ; =; 13; ; ; ; TeV, corresponding to an integrated luminosity of 138 fb; ; −; 1; ; , collected at the CERN LHC with the CMS detector. Events containing two leptons (electrons or muons) and a photon in the final state are considered. The fiducial cross section of; ; ; $$ textrm{t}overline{textrm{t}}upgamma $$; ; t; ; t; ¯; ; γ; ; ; ; is measured to be 137 ± 8 fb, in a phase space including events with a high momentum, isolated photon. The fiducial cross section of; ; ; $$ textrm{t}overline{textrm{t}}upgamma $$; ; t; ; t; ¯; ; γ; ; ; ; is also measured to be 56 ± 5 fb when considering only events where the photon is emitted in the production part of the process. Both measurements are in agreement with the theoretical predictions, of 126 ± 19 fb and 57 ± 5 fb, respectively. Differential measurements are performed at the particle and parton levels. Additionally, inclusive and differential ratios between the cross sections of; ; ; $$ textrm{t}overline{textrm{t}}upgamma $$; ; t; ; t; ¯; ; γ; ; ; ; and; ; ; $$ textrm{t}overline{textrm{t}} $$; ; t; ; t; ¯; ; ; ; ; production are measured. The inclusive ratio is found to be 0.0133 ± 0.0005, in agreement with the standard model prediction of 0.0127 ± 0.0008. The top quark charge asymmetry in; ; ; $$ textrm{t}overline{textrm{t}}upgamma $$; ; t; ; t; ¯; ; γ; ; ; ; production is also measured to be −0.012 ± 0.042, compatible with both the standard model prediction and with no asymmetry.;
