Sensitivity of jet quenching to the initial state in heavy-ion collisions

TL;DR

This paper develops analytical methods to understand how the initial state of the medium affects jet quenching in heavy-ion collisions, revealing that early-stage medium properties significantly influence jet suppression and asymmetry.

Contribution

It introduces resummation schemes for radiative energy loss in evolving backgrounds, improving the understanding of initial state effects on jet quenching.

Findings

Strong jet quenching requires medium equilibration time longer than mean free path.

Early-stage medium coupling impacts jet azimuthal asymmetry.

Analytical results highlight the importance of initial medium conditions.

Abstract

In heavy-ion collisions, nuclear matter is subjected to extreme conditions in a highly dynamical, rapidly evolving environment. This poses a tremendous challenge for calculating jet quenching observables. Current approaches rely on analytical results for static cases, introducing theoretical uncertainties and biases in our understanding of the pre-equilibrated medium. To address this issue, we employ resummation schemes to derive analytical rates for radiative energy loss in generic, evolving backgrounds. We investigate regimes where rare scattering and multiple scattering with the dynamical medium occurs, and extract relevant scales governing the in-medium emission rate of soft gluons. Our analysis indicates that strong jet quenching is only possible when the equilibration time of the medium is longer than its mean free path, highlighting the importance of medium modifications of jets in the earliest stages of heavy-ion collisions. We also demonstrate analytically that a medium evolution, which initially has a small coupling to jets, typically leads to a stronger jet azimuthal asymmetry at the same jet suppression factor.