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
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