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

The jet radial structure and particle transverse momentum (p(T)) composition within jets are presented in centrality-selected Pb-Pb collisions at root 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 vertical bar eta(chjet)vertical bar < 0.6 for transverse momenta P-T,P- (ch jet) = 30-120 GeV/c. Jet-hadron correlations in relative azimuth and pseudorapidity space (Delta phi/Delta eta) 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, chjet) = 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. (C) 2019 The Author(s). Published by Elsevier B.V.