Measurement of isolated-photon+jet correlations in PbPb collisions at $\sqrt{s} = 2.76\:\mathrm{TeV}$ with CMS

A measurement of the transverse momentum balance in isolated-photon+jet pairs in PbPb collisions is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from PbPb collisions at a $\sqrt{s_{NN}} = 2.76\:\mathrm{TeV}$, corresponding to an integrated luminosity of $150\:\mathrm{\mu b}^{-1}$. For events containing an isolated photon with $p_T^\gamma > 60\:\mathrm{GeV}/c$ and an associated jet with $p_T^\mathrm{Jet} > 30\:\mathrm{GeV}/c$, the photon+jet transverse momentum balance is studied as a function of collision centrality and compared to pp data and PYTHIA calculations. Using the isolated photon as the probe of the partonic energy at production, this measurement allows an unbiased characterization of the in-medium parton energy loss. With increasing collision centrality, a significant decrease in the ratio $p_T^\mathrm{Jet}/p_T^\gamma$ relative to the pp reference is observed.