Momentum imbalance of isolated photon-tagged jet production at RHIC and LHC

Abstract

In collisions of ultra-relativistic nuclei, photon-tagged jets provide a unique opportunity to compare jet production and modification due to parton shower formation and propagation in strongly-interacting matter at vastly different center-of-mass energies. We present first results for the cross sections of jets tagged by an isolated photon to ${\cal O}(\alpha_{\rm em} \alpha_s^2)$ in central Au+Au reactions with $\sqrt{s_{NN}}=200$ GeV at RHIC and central Pb+Pb reactions with $\sqrt{s_{NN}}=2.76$ TeV at LHC. We evaluate the increase in the transverse momentum imbalance of the observed $\gamma$+jet state, induced by the dissipation of the parton shower energy due to strong final-state interactions. Theoretical predictions to help interpret recent and upcoming experimental data are presented.