Performance and calibration of quark/gluon-jet taggers using 140 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The identification of jets originating from quarks or gluons, often referred to as quark/gluon tagging, plays an important role in various physics analyses at the Large Hadron Collider. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using $\sqrt{s} = 13$ TeV proton-proton collision data with an integrated luminosity of 140 fb$^{-1}$ collected by the ATLAS experiment. Two taggers are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.