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Title: | Observation of Medium-Induced Modifications of Jet Fragmentation in Pb-Pb Collisions at sNN =5.02 TeV Using Isolated Photon-Tagged Jets |
Authors: | Sirunyan, AM Tumasyan, A Adam, W Ambrogi, F Asilar, E Bergauer, T Brandstetter, J Brondolin, E Dragicevic, M Erö, J Escalante Del Valle, A Flechl, M Friedl, M Frühwirth, R Ghete, VM Grossmann, J Hrubec, J Jeitler, M König, A Krammer, N Krätschmer, I Liko, D Madlener, T Mikulec, I Pree, E Rad, N Rohringer, H Schieck, J Schöfbeck, R Spanring, M Spitzbart, D Taurok, A Waltenberger, W Wittmann, J Wulz, CE Zarucki, M Chekhovsky, V Mossolov, V Suarez Gonzalez, J De Wolf, EA Di Croce, D Janssen, X Lauwers, J Van De Klundert, M Van Haevermaet, H Van Mechelen, P Van Remortel, N Abu Zeid, S Blekman, F D'Hondt, J De Bruyn, I De Clercq, J Deroover, K Flouris, G Lontkovskyi, D Lowette, S Marchesini, I Moortgat, S Moreels, L Python, Q Skovpen, K Tavernier, S Van Doninck, W Van Mulders, P Van Parijs, I Beghin, D Bilin, B Brun, H Clerbaux, B De Lentdecker, G Delannoy, H Dorney, B Fasanella, G Favart, L Goldouzian, R Grebenyuk, A Kalsi, AK Lenzi, T Luetic, J Maerschalk, T Marinov, A Seva, T Starling, E Vander Velde, C Vanlaer, P Vannerom, D Yonamine, R Zenoni, F Cornelis, T Dobur, D Fagot, A Gul, M Khvastunov, I Poyraz, D Roskas, C |
Issue Date: | 2018 |
Publisher: | American Physical Society |
Citation: | Physical Review Letters |
Abstract: | 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 pjet T > 30 GeV=c in events containing an isolated photon with pγ T > 60 GeV=c, using charged tracks with transverse momentum ptrk 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. |
URI: | http://bura.brunel.ac.uk/handle/2438/17342 |
DOI: | http://dx.doi.org/10.1103/PhysRevLett.121.242301 |
ISSN: | 0031-9007 1079-7114 |
Appears in Collections: | Publications Publications |
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