Measurements of hard probes of the quark-gluon plasma with the ATLAS experiment at the LHC

ATLAS results on the production of high-transverse momentum probes in Pb+Pb and p+Pb collisions at the LHC are presented. The focus is on the jet measurements, which provide a useful tool to study the hot, dense and coloured matter created in ultra-relativistic heavy ion collisions. The ATLAS experiment has measured inclusive jet yields in pp and Pb+Pb collisions at sqrt(s_NN) = 2.76 TeV and in p+Pb collisions at sqrt(s_NN) = 5.02 TeV. The jet nuclear modification factor, RAA, is shown as a function of jet pT, rapidity and collision centrality. The RAA weakly increases with pT, shows no dependence on rapidity and smoothly decreases with the collision centrality. In 10% of the most central collisions, jet production is suppressed by a factor of two relative to pp yields scaled by the number of binary nucleonnucleon collisions. Charged-particle fragmentation functions of jets are also measured and ratios of fragmentation functions between di erent centrality intervals show a centrality-dependent modification. The jet measurements in p+Pb collisions show jet enhancement in peripheral collisions and suppression in central collisions as compared to the scaled pp jet yields. These modifications are most pronounced at forward rapidities and at large jet transverse momenta. Jet production at forward rapidities shows a scaling in the total jet energy, suggesting that the modification of jet production in p+Pb collisions may depend on the kinematics of the initial hard parton-parton scattering.