Abstract
This paper presents a measurement of jet fragmentation functions in 0.49 nb−1 of Pb+Pb collisions and 25 pb−1 of pp collisions at sNN=5.02 TeV collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultrarelativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in pp collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 and 398 GeV and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet transverse momentum. Yields of particles carrying a very large fraction of the jet momentum are also observed to be enhanced. Between these two enhancements of the fragmentation functions a suppression of particles carrying an intermediate fraction of the jet momentum is observed in Pb+Pb collisions. A small dependence of the modifications on jet rapidity is observed.18 MoreReceived 16 May 2018DOI:https://doi.org/10.1103/PhysRevC.98.024908Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasFragmentation into hadronsQuark & gluon jetsRelativistic heavy-ion collisionsNuclear Physics
Highlights
Ultrarelativistic nuclear collisions at the Large Hadron Collider (LHC) produce hot dense matter called the quark-gluon plasma (QGP); recent reviews can be found in Refs. [1,2]
In order to quantify the difference in the fragmentation functions between Pb+Pb and pp collisions, the ratios of D(z) and D(pT) distributions measured in Pb+Pb collisions to those measured in pp collisions, RD(z) and RD(pT), are shown in Figs. 12 and 13, respectively
√ofsN0N.4=9 nb−1 5.02 of Pb+Pb TeV using data collected with the ATLAS detector at the LHC in 2015
Summary
Ultrarelativistic nuclear collisions at the Large Hadron Collider (LHC) produce hot dense matter called the quark-gluon plasma (QGP); recent reviews can be found in Refs. [1,2]. Related phenomena were first observed at the Relativistic Heavy Ion Collider where the measurements were made with hadrons rather than reconstructed jets [10,11,12]. These observations imply that some of the energy of the parton showering process is transferred outside of the jet through its interaction with the QGP.
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