Medium-Induced Modification of Z -Tagged Charged Particle Yields in Pb+Pb Collisions at 5.02 TeV with the ATLAS Detector

Collaboration, ATLAS and Barton, A.E. and Bertram, I.A. and Borissov, G. and Bouhova-Thacker, E.V. and Fox, H. and Henderson, R.C.W. and Jones, R.W.L. and Kartvelishvili, V. and Long, R.E. and Love, P.A. and Muenstermann, D. and Sanderswood, Izaac and Smizanska, M. and Tee, A.S. and Walder, J. and Wharton, A.M. and Whitmore, B.W. and Yexley, Melissa (2021) Medium-Induced Modification of Z -Tagged Charged Particle Yields in Pb+Pb Collisions at 5.02 TeV with the ATLAS Detector. Physical review letters, 126 (7): 072301. ISSN 1079-7114

Abstract

The yield of charged particles opposite to a Z boson with large transverse momentum (pT) is measured in 260 pb-1 of pp and 1.7 nb-1 of Pb+Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how their showers are modified as they propagate through the quark-gluon plasma created in Pb+Pb collisions. Compared with pp collisions, charged-particle yields in Pb+Pb collisions show significant modifications as a function of charged-particle pT in a way that depends on event centrality and Z boson pT. The data are compared with a variety of theoretical calculations and provide new information about the medium-induced energy loss of partons in a pT regime difficult to measure through other channels. © 2021 CERN.