Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at 𝑠𝑁𝑁‾‾‾‾√= 5.02 TeV Using Isolated Photon-Tagged Jets
Sirunyan, Albert M.
Meinhard, Maren T.
Sanz Becerra, Diego A.
Tavolaro, Vittorio R.
Vesterbacka Olsson, Minna L.
Zhu, De Hua
- Journal Article
Rights / licenseCreative Commons Attribution 4.0 International
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 pTjet>30 GeV/c in events containing an isolated photon with pTγ>60 GeV/c, using charged tracks with transverse momentum pTtrk>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. Show more
Journal / seriesPhysical Review Letters
Pages / Article No.
PublisherAmerican Physical Society
Organisational unit03593 - Dissertori, Günther / Dissertori, Günther
03904 - Wallny, Rainer / Wallny, Rainer
08803 - Grab, Christoph (Tit.Prof.)
09631 - Shchutska, Lesya (ehemalig) / Shchutska, Lesya (former)
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