Tracking Energy Loss in Heavy Ion Collisions

TL;DR

This paper introduces a new theoretical framework for describing energy loss in heavy ion collisions by linking it to the renormalization group evolution of track functions, improving the understanding of jet quenching.

Contribution

It proposes a novel formalism connecting energy loss functions with track functions, enabling perturbative QCD analysis of jet substructure in heavy ion collisions.

Findings

Energy loss functions can be studied via renormalization group evolution.

The approach relates energy loss to track function formalism.

Application to energy correlators enhances theoretical modeling.

Abstract

The main modification to high $p_t$ jets evolving in the quark gluon plasma is the depletion of their energy to the thermal background. Despite the prominent role played by energy loss effects in jet quenching, their theoretical description is still limited, being, to a large extent, driven by phenomenological considerations. As the field moves towards the measurement of multi-scale jet substructure observables, it is necessary to develop new field theoretic techniques to describe energy loss. In this letter, we highlight a formal similarity between energy loss, and the renormalization group based track function formalism for computing jet substructure observables on charged particles. We introduce an energy loss function, $L_i(x)$, tracking the energy fraction $x$ flowing from an initial hard parton $i$ down to the measured hadrons, and show that its renormalization group evolution can be studied in perturbative QCD, and is related to that of the track functions. The features of this new approach are illustrated in the computation of projected energy correlators, opening the window to a better theoretical treatment of these observables in heavy ion collisions.