Abstract
We present measurements of the jet fragmentation functions and transverse momentum profiles (shapes) in PbPb collisions at s NN = 2.76 TeV per nucleon-pair center-of-mass energy with the CMS detector. Jets are reconstructed by the anti- k T sequential clustering algorithm with a resolution parameter of 0.3, using particle-flow objects that combine tracking and calorimetric information. In this proceedings the jet properties of inclusive jets with transverse momentum p T > 100 GeV / c in PbPb collisions are measured for reconstructed charged particles with p T > 1 GeV / c in a cone of radius Δ ϕ 2 + Δ η 2 = 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a center-of-mass energy of s NN = 2.76 TeV corresponding to an integrated luminosity of 150 μb −1 is used. The results for PbPb collisions as a function of collision centrality are compared to reference distributions based on the full 2013 pp statistics collected at the same collision energy. Centrality-dependent modifications of the fragmentation functions and shapes are revealed.
Highlights
Hard probes - processes involving scatterings with large momentum transfer - and their modification in PbPb collisions with respect to pp collisions, can be used to study the transport properties of the hot quark-gluon plasma (QGP) medium created in heavy ion collisions at ultra-relativistic energies [1]
We present measurements of the jet fragmentation functions and transverse momentum profiles in PbPb collisions at 2.76
It is evident in the suppression of high pT charged hadrons and jets, as well as in the associated yield in two-particle correlations measurements [5], which is accompanied by an enhancement of low pT hadrons, suggesting a softening of jet fragmentations
Summary
Hard probes - processes involving scatterings with large momentum transfer - and their modification in PbPb collisions with respect to pp collisions, can be used to study the transport properties of the hot quark-gluon plasma (QGP) medium created in heavy ion collisions at ultra-relativistic energies [1]. It is well established that the parton energy loss is a consequence of the modification of the hard-scattering processes in the final state of the heavy ion collisions at RHIC and LHC [2,3,4] It is evident in the suppression of high pT charged hadrons and jets, as well as in the associated yield in two-particle correlations measurements [5], which is accompanied by an enhancement of low pT hadrons, suggesting a softening of jet fragmentations. In heavy-ion collisions, particles from the underlying event that happen to fall inside the jet cone would affect the measurements This contribution is subtracted following a procedure previously employed by CMS in the measurement of the jet fragmentation function, using a method called the η-reflection method [7]. The minimum transverse momentum for tracks entering the analysis is set to 1 GeV/c
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