Measurement of the charged-particle multiplicity inside jets from [equation] [equation] ?ppcollisions with the ATLAS detector

摘要

The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This paper presents a measurement of the average number of charged particles with (p_ ext {T}>500)({mathrm{MeV}})?inside high-momentum jets in dijet events using 20.3 fb(^{-1}) of data recorded with the ATLAS detector in pp collisions at (sqrt{s}=8)?({mathrm{TeV}})?collisions at the LHC. The jets considered have transverse momenta from 50?({mathrm{GeV}})?up to and beyond 1.5 ({mathrm{TeV}}). The reconstructed charged-particle track multiplicity distribution is unfolded to remove distortions from detector effects and the resulting charged-particle multiplicity is compared to several models. Furthermore, quark and gluon jet fractions are used to extract the average charged-particle multiplicity for quark and gluon jets separately.