Charged-particle nuclear modification factors in PbPbfand pPb collisions at √sNN = 5.02 TeV

CMS Collaboration

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The spectra of charged particles produced within the pseudorapidity window ΙηΙ < 1 at √sNN = 5.02 TeV are measured using 404 µb-1 of PbPb and 27.4 pb-1 of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < pT < 400 GeV in pp and 0.7 < pT < 400 GeV in PbPb collisions. The corresponding nuclear modication factor, RAA, is measured in bins of collision centrality. The RAA in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the pT region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest pT measured, and approaches unity in the vicinity of pT = 200 GeV. The RAA is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modication factor, RpA, up to 120 GeV. For pT > 20 GeV, RpA exhibits weak momentum dependence and shows a moderate enhancement above unity.
Original languageEnglish
Article number039
Number of pages45
JournalJournal of High Energy Physics
Issue number4
Publication statusPublished - 2017
Externally publishedYes


  • Heavy Ion Experiments
  • Quark Gluon Plasma
  • Relativistic heavy ion physics

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