Jet asymmetry and momentum imbalance from $2 \to 2$ and $2 \to 3$ partonic processes in relativistic heavy-ion collisions

TL;DR

This paper investigates how parton energy loss in quark-gluon plasma affects jet asymmetry and momentum imbalance in heavy-ion collisions, incorporating LO $2 o 2$ and $2 o 3$ processes and hydrodynamic energy deposition models.

Contribution

It introduces a comprehensive model combining LO partonic processes with hydrodynamic energy loss to explain jet asymmetry data from CMS in heavy-ion collisions.

Findings

Shape of jet asymmetry explained by parton energy loss.

Including $2 o 3$ processes improves data agreement.

Model fits CMS data with specific energy loss parameters.

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 $\Delta{\mathcal{E}}$.