Measurement of Jet pT correlations in Pb+Pb and pp collisions at √sNN = 2.76 TeV with the ATLAS detector


Measurements of dijet pT correlations in Pb+Pb and pp collisions at a nucleon–nucleon centre-of-mass energy of √sNN= 2.76 TeV are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb+Pb and pp data samples corresponding to integrated luminosities of 0.14 nb−1 and 4.0 pb−1, respectively. Jets are reconstructed using the anti-kt algorithm with radius parameter values R = 0.3 and R = 0.4. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb+Pb collisions. The leading and sub-leading jet transverse momenta are denoted pT1 and pT2. An unfolding procedure is applied to the two-dimensional (pT1, pT2) distributions to account for experimental effects in the measurement of both jets. Distributions of (1/N)dN/dxJ, where xJ= pT2/pT1, are presented as a function of pT1 and collision centrality. The distributions are found to be similar in peripheral Pb+Pb collisions and pp collisions, but highly modified in central Pb+Pb collisions. Similar features are present in both the R =0.3 and R = 0.4 results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models. © 2017 The Author. Published by Elsevier B.V.



Transverse momentum, Lead-lead interactions, Proton-proton interactions, Jets (Nuclear physics), Partons


CC BY 4.0 (Attribution), ©2017 CERN, for the ATLAS Collaboration