Jet suppression and azimuthal anisotropy at RHIC and LHC

TL;DR

This paper investigates how jet suppression and azimuthal anisotropy depend on jet cone angle and medium properties in heavy-ion collisions at RHIC and LHC, revealing the role of the coherence angle in jet quenching.

Contribution

It introduces a detailed calculation of jet suppression and azimuthal anisotropy incorporating the IOE framework and realistic medium effects, highlighting the impact of the coherence angle on jet modification.

Findings

Jet suppression shows mild cone angle dependence at RHIC and LHC.

Jet azimuthal anisotropy $v_2$ varies with centrality and cone angle.

Sequential collapse of $v_2$ for moderate $R$ jets as centrality decreases.

Abstract

Jets are multi-partonic systems that develop before interactions with the quark-gluon plasma set in and lead to energy loss and modifications of their substructure. Jet modification depends on the degree to which the medium can resolve the internal jet structure that is dictated by the physics of coherence governed by a critical angle $\theta_c$. Using resummed quenching weights that incorporate the IOE framework for medium-induced radiation and embedding the system into a realistic heavy-ion environment we compute the dependence of jet suppression on the cone angle $R$ of the jet, both at RHIC and the LHC. At RHIC kinematics we see a very mild cone angle dependence for the range of $R$ studied, similar to what was found at the LHC. We also present results for the jet azimuthal anisotropy $v_2$ as a function of $R$. We observe that as centrality is decreased, $v_2$ for moderate $R$ jets sequentially collapse towards the result for small $R = 0.1$. The reason of this sequential grouping is the evolution of $\theta_c$ with centrality due to its strong dependence on the in-medium traversed length. For jets with $R > \theta_c$, traversing shorter lengths within the medium will make a larger difference than for jets with $R < \theta_c$, since the size of the resolved phase-space over which quenching weights are resummed will be reduced. For this reason, $v_2(R)$ is quite sensitive to the typical value of $\theta_c$ at a given centrality.