Yue Shi Lai (Massachusetts Inst. of Technology (US))
The first measurement of the transverse momentum (pT) imbalance of isolated-photon+jet pairs in relativistic heavy ion collisions is reported. The analysis uses data from PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair and corresponding to an integrated luminosity of 150/ub recorded by the CMS experiment at the LHC in 2011. For events containing an isolated photon with transverse momentum pT > 60 GeV/c and an associated jet with pT > 30 GeV/c, the photon–jet pT imbalance is studied as a function of collision centrality and compared to pp data and PYTHIA calculations at the same center-of-mass energy. Using the pT of the isolated photon as an estimate of the energy of the associated parton at production, this measurement allows an unbiased characterization of the in-medium parton energy loss.
Collaboration CMS (CERN)