Measurement of jet radial profiles in Pb–Pb collisions at sNN=2.76 TeV

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The jet radial structure and particle transverse momentum (p T) composition within jets are presented in centrality-selected Pb–Pb collisions at s NN=2.76 TeV. Track-based jets, which are also called charged jets, were reconstructed with a resolution parameter of R=0.3 at midrapidity |η ch jet|<0.6 for transverse momenta p T,ch jet=30–120 GeV/c. Jet–hadron correlations in relative azimuth and pseudorapidity space (Δφ,Δη) are measured to study the distribution of the associated particles around the jet axis for different p T,assoc-ranges between 1 and 20 GeV/c. The data in Pb–Pb collisions are compared to reference distributions for pp collisions, obtained using embedded PYTHIA simulations. The number of high-p T associate particles (4<p T,assoc<20 GeV/c) in Pb–Pb collisions is found to be suppressed compared to the reference by 30 to 10%, depending on centrality. The radial particle distribution relative to the jet axis shows a moderate modification in Pb–Pb collisions with respect to PYTHIA. High-p T associate particles are slightly more collimated in Pb–Pb collisions compared to the reference, while low-p T associate particles tend to be broadened. The results, which are presented for the first time down to p T,ch jet=30 GeV/c in Pb–Pb collisions, are compatible with both previous jet–hadron-related measurements from the CMS Collaboration and jet shape measurements from the ALICE Collaboration at higher p T, and add further support for the established picture of in-medium parton energy loss.


Original languageEnglish
Pages (from-to)204-219
Number of pages16
JournalPhysics Letters B
Early online date12 Jul 2019
Publication statusPublished - 10 Sep 2019

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