Using hard dihadron correlations to constrain elastic energy loss

Abstract

One contribution to the energy loss of hard partons propagating through a medium as created in ultrarelativistic heavy-ion (A-A) collisions are elastic scattering processes with medium constituents. The magnitude of this energy loss contribution depends crucially on the effective mass of the medium constituents - in the limit of non-recoiling static scattering centers, elastic energy loss vanishes. Thus, it is important to constrain the amount of elastic energy loss in order to gain information about the nature of the degrees of freedom in the medium as resolved by a hard parton. So far, the relative fraction of elastic (or rather incoherent) energy loss has been constrained from above by using pathlength dependent observables. However, using the observation that subleading gluon energy dissipation into the medium is probed by some observables, such as hard dihadron correlations or the dijet asymmetry, a constraint from below can also be found. In this work, this idea is worked out within the in-medium shower evolution Monte Carlo (MC) code YaJEM-D.