Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at √s[subscript NN] = 5.02 TeV Using Isolated Photon-Tagged Jets
Author(s)
CMS Collaboration; Abercrombie, Daniel Robert; Allen, Brandon Leigh; Azzolini, Virginia; Barbieri, Richard Alexander; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Harris, Philip Coleman; Hsu, Dylan George; Hu, Miao; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Lee, Yen-Jie; Levin, Amy Elizabeth; Luckey Jr, P David; Maier, Benedikt; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Siddharth Madhavan; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Sumorok, Konstanty C; Tatar, Kaya; Velicanu, Dragos Alexandru; Wang, Jing; Wang, Ta-Wei; Wyslouch, Boleslaw; ... Show more Show less
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Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with p[superscript jet][subscript T] > 30 GeV/c in events containing an isolated photon with p[superscript γ][subscript T] > 60 GeV/c, using charged tracks with transverse momentum p[superscript trk][subscript T] > 1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial pT and azimuthal angle of the parton whose shower produced the jet. For central Pb-Pb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central Pb-Pb events show an excess (depletion) of low (high) pT particles, with a transition around 3 GeV/c. This measurement shows for the first time the in-medium shower modifications of partons (quark dominated) with well-defined initial kinematics. It constitutes a new well-controlled reference for testing theoretical models of the parton passage through the quark-gluon plasma.
Date issued
2018-12Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering; Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Laboratory for Nuclear ScienceJournal
Physical Review Letters
Publisher
American Physical Society
Citation
Sirunyan, A. M. et al. “Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at √s[subscript NN] = 5.02 TeV Using Isolated Photon-Tagged Jets.” Physical Review Letters 121, 24 (December 2018): 242301 © 2018 CERN, for the CMS Collaboration
Version: Final published version
ISSN
0031-9007
1079-7114