Measurement of jet fragmentation in PbPb and pp collisions at sNN−−−√=2.76 TeV

CMS Collaboration; Chatrchyan, S; Sirunyan, A M; Tumasyan, A; Khachatryan, V; Canelli, F; Chiochia, V; De Cosa, A; Hinzmann, A; Hreus, T; Ivova Rikova, M; Kilminster, B; Ngadiuba, J; Robmann, P; Ronga, F J; Taroni, S; Verzetti, M; Yang, Y; Mejias, B; Amsler, C; Favaro, C; Snoek, H; et al (2014). Measurement of jet fragmentation in PbPb and pp collisions at sNN−−−√=2.76 TeV. Physical Review C (Nuclear Physics), 90(024908):online.

Abstract

The jet fragmentation function of inclusive jets with transverse momentum pT above 100GeV/c in PbPb collisions has been measured using reconstructed charged particles with pT above 1GeV/c in a cone of radius 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a nucleon-nucleon center-of-mass energy of sNN=2.76TeV corresponding to an integrated luminosity of 150μb−1 is used. The results for PbPb collisions as a function of collision centrality and jet transverse momentum are compared to reference distributions based on pp data collected at the same center-of-mass energy in 2013, with an integrated luminosity of 5.3pb−1. A centrality-dependent modification of the fragmentation function is found. For the most central collisions, a significant enhancement is observed in the PbPb/pp fragmentation function ratio for charged particles with pT less than 3GeV/c. This enhancement is observed for all jet pT bins studied.

Abstract

The jet fragmentation function of inclusive jets with transverse momentum pT above 100GeV/c in PbPb collisions has been measured using reconstructed charged particles with pT above 1GeV/c in a cone of radius 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a nucleon-nucleon center-of-mass energy of sNN=2.76TeV corresponding to an integrated luminosity of 150μb−1 is used. The results for PbPb collisions as a function of collision centrality and jet transverse momentum are compared to reference distributions based on pp data collected at the same center-of-mass energy in 2013, with an integrated luminosity of 5.3pb−1. A centrality-dependent modification of the fragmentation function is found. For the most central collisions, a significant enhancement is observed in the PbPb/pp fragmentation function ratio for charged particles with pT less than 3GeV/c. This enhancement is observed for all jet pT bins studied.

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