Jet shape and fragmentation function measurements with CMS

Abstract

We present measurements of the jet fragmentation functions and transverse momentum profiles (shapes) in PbPb collisions at 2.76 TeV per nucleon-pair center of mass energy with the CMS detector. Jets are reconstructed by the anti-k T sequential clustering algorithm with a resolution parameter of 0.3, using particle-flow objects that combine tracking and calorimetric information. In this talk the jet properties of inclusive jets with transverse momentum p T > 100 GeV/c in PbPb collisions are measured for reconstructed charged particles with p T > 1 GeV/c in a cone of radius ∆φ 2 + ∆η 2 = 0.3 around the jet axis. A data sample of collisions collected in 2011 at a center-of-mass energy of √ s N N = 2.76 TeV corresponding to an integrated luminosity of 150 µb −1 is used. The results for PbPb collisions as a function of collision centrality are compared to reference distributions based on the full 2013 pp statistics collected at the same collision energy. Centrality-dependent modifications of the fragmentation functions and shapes are revealed. Department of Physics and Astronomy, Vanderbilt University, Nashville, TN37235, USA AbstractWe present measurements of the jet fragmentation functions and transverse momentum profiles (shapes) in PbPb collisions at 2.76 TeV per nucleon-pair center of mass energy with the CMS detector. Jets are reconstructed by the anti-k T sequential clustering algorithm with a resolution parameter of 0.3, using particle-flow objects that combine tracking and calorimetric information. In this talk the jet properties of inclusive jets with transverse momentum p T > 100 GeV/c in PbPb collisions are measured for reconstructed charged particles with p T > 1 GeV/c in a cone of radius ∆φ 2 + ∆η 2 = 0.3 around the jet axis. A data sample of PbPb collisions collected in 2011 at a center-of-mass energy of √ s NN = 2.76 TeV corresponding to an integrated luminosity of 150 µb −1 is used. The results for PbPb collisions as a function of collision centrality are compared to reference distributions based on the full 2013 pp statistics collected at the same collision energy. Centrality-dependent modifications of the fragmentation functions and shapes are revealed.

Physics perspectives of heavy-ion collisions at very high energy

“…One can see a considerable enhancement of jet shapes in heavy-ion collisions relative to those in p+p in the region when r → R due to induced gluon radiation while there is some depletion of jet energy distribution at intermediate r due to fixed total jet energy. Such a feature has been observed in heavy-ion collisions at LHC [167] and should provide information on jet-medium interaction at future high-energy heavy-ion colliders.…”