Jet asymmetry and momentum imbalance from2→2and2→3partonic processes in relativistic heavy-ion collisions

Abstract

We study momentum imbalance as a function of jet asymmetry in high-energy heavy-ion collisions. To implement parton production during the collision, we include all Leading Order (LO) $2\to 2$ and $2\to 3$ parton processes in pQCD. The produced partons lose energy within the quark gluon plasma and hadronize collinearly when they leave it. The energy and momentum deposited into the plasma is described using linear viscous hydrodynamics with a constant energy loss per unit length and a total energy loss given by a Gaussian probability centered around a mean value $\bar{\mathcal{E}}$ and a half-width $\Delta{\mathcal{E}}$. We argue that the shape of the asymmetry observed by the CERN-CMS Collaboration can indeed be attributed to parton energy loss in the medium and that a good description of data is achieved when one includes a slight enhancement coming from the contribution of $2\to 3$ parton processes that modifies the asymmetry distribution of the dijet events. We compare our results to CMS data for the most central collisions and study different values for $\bar{\mathcal{E}}$ and $\Delta{\mathcal{E}}$.