Abstract
Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the Compact Muon Solenoid (CMS) detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7μb−1. Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cutoff used in this study (jet pT=120 GeV/c) up to the statistical limit of the available data sample (jet pT≈210 GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet.8 MoreReceived 10 February 2011DOI:https://doi.org/10.1103/PhysRevC.84.024906This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.©2011 CERN, for the CMS Collaboration
Highlights
High-energy collisions of heavy ions allow the fundamental theory of the strong interaction—quantum chromodynamics (QCD)—to be studied under extreme temperature and density conditions
Jets are identified primarily using the energy deposited in the leadtungstate crystal electromagnetic calorimeter (ECAL) and the brass and scintillator hadron calorimeter (HCAL) covering |η| < 3
PbPTbhecoCllMisSiondsetaetct√orsNhNas=be2e.n76usTeedVt.oJesttusdwyejreet production in reconstructed using primarily the calorimeter information in a data sample corresponding to an integrated luminosity of Lint = 6.7 μb−1
Summary
High-energy collisions of heavy ions allow the fundamental theory of the strong interaction—quantum chromodynamics (QCD)—to be studied under extreme temperature and density conditions. A new form of matter [1,2,3,4] formed at energy densities above ∼1 GeV/fm is predicted in lattice QCD calculations [5] This quark-gluon plasma (QGP) consists of an extended volume of deconfined and chirally symmetric quarks and gluons. One of the first experimental signatures suggested for QGP studies was the suppression of high-transversemomentum (pT) hadron yields resulting from energy loss suffered by hard-scattered partons passing through the medium [6]. This parton energy loss is often referred to as “jet quenching.”. Preliminary results for fully reconstructed jets at RHIC, measured in AuAu
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