Interpreting single jet measurements in Pb plus Pb collisions at the LHC

Results are presented from a phenomenological analysis of recent measurements of jet suppression and modifications of jet fragmentation functions in Pb+Pb collisions at the LHC. Particular emphasis is placed on the impact of the differences between quark and gluon jet quenching on the transverse momentum (p(T)(jet)) dependence of the jet R-AA and on the fragmentation functions, D(z). Primordial quark and gluon parton distributions were obtained from PYTHIA8 and were parameterized using simple power-law functions and extensions to the power-law function which were found to better describe the PYTHIA8 parton spectra. Asimple model for the quark energy loss based on the shift formalism is used to model R-AA and D(z) using both analytic results and using direct Monte-Carlo sampling of the PYTHIA parton spectra. The model is capable of describing the full p(T)(jet), rapidity, and centrality dependence of the measured jet R-AA using three effective parameters. A key result from the analysis is that the D(z) modifications observed in the data, excluding the enhancement at low-z, may result primarily from the different quenching of the quarks and gluons. The model is also capable of reproducing the charged hadron R-AA at high transverse momentum. Predictions are made for the jet R-AA at large rapidities where it has not yet been measured and for the rapidity dependence of D(z).