Hard Probe Observables of Jet Quenching in the Monte Carlo Event Generator JEWEL

Abstract

The jet quenching effects of including recoil partons from interactions of high momentum partons with the QGP in Pb+Pb events are studied in the JEWEL Monte Carlo Event Generator. Momentum balance in the model shows that excluding recoil partons leads to a net momentum imbalance on the order of tens of GeV/c, indicating the necessity to include recoil partons in observables that depend on momentum conservation. When calculating the nuclear modification factor RAA, the generation of recoil hadrons that result from the hadronization of recoil partons requires a background subtraction procedure to be implemented due to the high number of recoil tracks as compared to benchmark p+p events. Furthermore, the non-uniform distribution of recoil tracks in pseudorapidity presents both a conceptual curiosity and exceptional challenges in sampling the recoil track background, in particular, choosing the region in the φ, η plane to sample for the density of jet transverse momentum. Several regions are compared for cone radii used in jet finding ranging from R = 0.2 to R = 0.5. We find that including recoil partons leads to a dependence of the nuclear modification factor on the cone radius that is not observed when recoil partons are excluded.