Picturing QCD jets in anisotropic matter: from jet shapes to Energy Energy Correlators

TL;DR

This paper investigates how anisotropic quark-gluon plasma affects jet observables, revealing directional energy redistribution and azimuthal dependencies, with implications for jet tomography in nuclear matter.

Contribution

It provides leading order calculations of jet observables in anisotropic matter, highlighting the azimuthal dependence of jet shapes and the robustness of energy correlation measurements.

Findings

Energy distribution shifts towards the largest matter anisotropy

Jet mass and girth show azimuthal dependence

Energy correlations are less affected by vacuum suppression

Abstract

Recent theoretical developments in the description of jet evolution in the quark gluon plasma have allowed to account for the effects of hydrodynamic gradients in the medium modified jet spectra. These constitute a crucial step towards using jets as tomographic probes of the nuclear matter they traverse. In this work, we complement these studies by providing leading order calculations of widely studied jet observables, taking into account matter anisotropies. We show that the energy distribution inside a jet is pushed towards the direction of the largest matter anisotropy, while the away region is depleted. As a consequence, the jet mass and girth gain a non-trivial azimuthal dependence, with the average value of the distribution increasing along the direction of largest gradients. However, we find that, for these jet shapes, matter anisotropic effects can be potentially suppressed by vacuum Sudakov factors. We argue that the recently proposed measurements of energy correlations within jets do not suffer from such effects, with the azimuthal dependence being visible in a large angular window, regardless of the shape of the distribution.