Measurement of jet track functions in 𝑝�𝑝� collisions at √𝑠� = 13 TeV with the ATLAS detector

Abstract

Measurements of jet substructure are key to probing the energy frontier at colliders, and many of them use trackbasedobservables which take advantage of the angular precision of tracking detectors. Theoretical calculationsof track-based observables require 'track functions', which characterize the transverse momentum fraction 𝑟𝑞carried by charged hadrons from a fragmenting quark or gluon. This letter presents a direct measurement of𝑟𝑞 distributions in dijet events from the 140 fb-1 of proton-proton collisions atSQUARE ROOT𝑠 = 13 TeV recorded with theATLAS detector. The data are corrected for detector effects using machine-learning methods. The scale evolutionof the moments of the 𝑟𝑞 distribution is sensitive to non-linear renormalization group evolution equations of QCD,and is compared with analytic predictions. When incorporated into future theoretical calculations, these resultswill enable a precision program of theory-data comparison for track-based jet substructure observables.