Medium modification of the shape of small-radius jets in central Pb-Pb collisions at $\sqrt{{\textit s}_{\rm NN}}=2.76$ TeV

S. Acharya , Łukasz Graczykowski , Monika Jakubowska , Małgorzata Janik , Adam Kisiel , Julian Myrcha , Jeremi Niedziela , Janusz Oleniacz , Jan Pluta , Przemysław Rokita , Krystian Rosłon , Tomasz Trzciński , Hanna Zbroszczyk


We present the measurement of a new set of jet shape observables for track-based jets in central Pb-Pb collisions at $\sqrt{{\textit s}_{\rm NN}}=2.76$ TeV. The set of jet shapes includes the first radial moment or angularity, g; the momentum dispersion, pTD; and the difference between the leading and sub-leading constituent track transverse momentum, LeSub. These observables provide complementary information on the jet fragmentation and can constrain different aspects of the theoretical description of jet-medium interactions. The jet shapes were measured for a small resolution parameter R = 0.2 and were fully corrected to particle level. The observed jet shape modifications indicate that in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by PYTHIA calculations, which were validated with the measurements of the jet shapes in proton-proton collisions at $\sqrt{{\textit s}}=7$ TeV. The comparison of the measured distributions to templates for quark and gluon-initiated jets indicates that in-medium fragmentation resembles that of quark jets in vacuum. We further argue that the observed modifications are not consistent with a totally coherent energy loss picture where the jet loses energy as a single colour charge, suggesting that the medium resolves the jet structure at the angular scales probed by our measurements $(R = 0.2)$. Furthermore, we observe that small-R jets can help to isolate purely energy loss effects from other effects that contribute to the modifications of the jet shower in medium such as the correlated background or medium response.
Collective authorALICE collaboration
Author S. Acharya - [Variable Energy Cyclotron Centre India]
S. Acharya,,
, Łukasz Graczykowski (FP / NPD)
Łukasz Graczykowski,,
- Nuclear Physics Division
, Monika Jakubowska (FoEE / ICIE)
Monika Jakubowska,,
- The Institute of Control and Industrial Electronics
, Małgorzata Janik (FP / NPD)
Małgorzata Janik,,
- Nuclear Physics Division
, Adam Kisiel (FP / NPD)
Adam Kisiel,,
- Nuclear Physics Division
, Julian Myrcha (FEIT / IN)
Julian Myrcha,,
- The Institute of Computer Science
, Jeremi Niedziela (FP / NPD)
Jeremi Niedziela,,
- Nuclear Physics Division
, Janusz Oleniacz (FP / NPD)
Janusz Oleniacz,,
- Nuclear Physics Division
, Jan Pluta (FP / NPD)
Jan Pluta,,
- Nuclear Physics Division
, Przemysław Rokita (FEIT / IN)
Przemysław Rokita,,
- The Institute of Computer Science
et al.`
Total number of authors1017
Journal seriesJournal of High Energy Physics, ISSN 1029-8479 [1126-6708], (A 40 pkt)
Issue year2018
Publication size in sheets1.35
Keywords in EnglishHeavy Ion Experiments
ASJC Classification3106 Nuclear and High Energy Physics
projectDevelopment of new algorithms in the areas of software and computer architecture, artificial intelligence and information systems and computer graphics . Project leader: Arabas Jarosław, , Phone: +48 22 234 7432, start date 01-08-2018, planned end date 30-09-2019, II/2018/DS/1, Implemented
WEiTI Działalność statutowa
Languageen angielski
JHEP10(2018)139.pdf 1.13 MB
Score (nominal)40
ScoreMinisterial score = 40.0, 18-04-2019, ArticleFromJournal
Ministerial score (2013-2016) = 40.0, 18-04-2019, ArticleFromJournal
Publication indicators WoS Citations = 0; Scopus Citations = 1; Scopus SNIP (Source Normalised Impact per Paper): 2017 = 1.083; WoS Impact Factor: 2017 = 5.541 (2) - 2017=4.807 (5)
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