Measurements of observables sensitive to colour reconnection in tt(bar) events with the ATLAS detector at √s = 13TeV
Abstrakt
Ameasurement of observables sensitive to effectsof colour reconnection in top-quark pair-production events is presented using 139 fb-1 of 13TeV proton-proton collision data collected by the ATLAS detector at the LHC.
Events are selected by requiring exactly one isolated electron and one isolated muon with opposite charge and two or three jets, where exactly two jets are required to be btagged.
For the selected events, measurements are presented for the charged-particle multiplicity, the scalar sum of the transverse momenta of the charged particles, and the same scalar sum in bins of charged-particle multiplicity. These observables are unfolded to the stable-particle level, thereby correcting for migration effects due to finite detector resolution, acceptance and efficiency effects. The particle-level measurements are compared with different colour reconnectionmodels inMonte Carlo generators. Thesemeasurements disfavour some of the colour reconnection models and provide inputs to future optimisation of the parameters in Monte Carlo generators.