Measurement of Inclusive Jet Charged-Particle Fragmentation Functions in Pb+Pb Collisions at √s[subscript NN] = 2.76 TeV with the ATLAS Detector

Abstract

Measurements of charged-particle fragmentation functions of jets produced in ultra-relativistic nuclear collisions can provide insight into the modification of parton showers in the hot, dense medium created in the collisions. ATLAS has measured jets in √s[subscript NN] = 2.76 TeV Pb+Pb collisions at the LHC using a data set recorded in 2011 with an integrated luminosity of 0.14 nb[superscript −1]. Jets were reconstructed using the anti-[subscript kt] algorithm with distance parameter values R= 0.2, 0.3, and 0.4. Distributions of charged-particle transverse momentum and longitudinal momentum fraction are reported for seven bins in collision centrality for R= 0.4 jets with p[jet over T] > 100 GeV. Commensurate minimum [subscript pT] values are used for the other radii. Ratios of fragment distributions in each centrality bin to those measured in the most peripheral bin are presented. These ratios show a reduction of fragment yield in central collisions relative to peripheral collisions at intermediate z values, 0.04 ≲ z ≲ 0.2, and an enhancement in fragment yield for z ≲ 0.04. A smaller, less significant enhancement is observed at large z and large [subscript pT] in central collisions.