Observation of medium induced modifications of jet fragmentation in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV using isolated-photon-tagged jets

Abstract

Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and PbPb 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 p${}_{\mathrm{T}}^{\text{jet}}>$ 30 GeV in events containing an isolated photon with p${}_{\mathrm{T}}^{\gamma }>$ 60 GeV, using charged tracks with transverse momentum p${}_{\mathrm{T}}^{\text{trk}}>$ 1 GeV in a cone around the jet axis. The association with an isolated photon constrains the initial p${}_{\mathrm{T}}$ and azimuthal angle of the parton whose shower produced the jet. For central PbPb 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 PbPb events show an excess (depletion) of low (high) p${}_{\mathrm{T}}$ particles, with a transition around 3 GeV. 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 QGP.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables, including additional supplementary figures, can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-16-014 (CMS Public Pages)

References in corpus (16)

• An Introduction to PYTHIA 8.2
• Glauber Modeling in High Energy Nuclear Collisions
• Particle-flow reconstruction and global event description with the CMS detector
• Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV
• Studies of jet quenching using isolated-photon + jet correlations in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
• Measurements of the Nuclear Modification Factor for Jets in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV with the ATLAS Detector
• Measurement of jet fragmentation in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
• Measurement of jet suppression in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Azimuthal anisotropy of charged particles at high transverse momenta in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions
• The physics of $Z^0/{\gamma }^{\ast }$-tagged jets at the LHC
• Study of jet quenching with Z+jet correlations in PbPb and pp collisions at sqrt(s[NN]) = 5.02 TeV
• Measurement of jet fragmentation in Pb+Pb and $pp$ collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV with the ATLAS detector
• Study of jet quenching with isolated-photon+jet correlations in PbPb and pp collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV
• Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Vector boson-tagged jet production in heavy ion collisions at the LHC

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