Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at s NN = 2.76 ? TeV with the ATLAS detector

摘要

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 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 ?1 . Jets were reconstructed using the anti- k t 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 T jet 100 ? GeV . Commensurate minimum p T 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 p T in central collisions.