Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at √s_NN = 2.76 TeV

An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (p_T) surrounding dijet systems is measured by selecting charged particles in different ranges of p_T and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the p_T asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-k_T jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the p_T imbalance compensated by an excess of low-p_T particles at large angles from the jet axes.