A dynamical implementation of colour coherence for quenched jets in JEWEL

TL;DR

This paper introduces a dynamic implementation of colour coherence in the JEWEL event generator, affecting jet evolution in dense media by determining when structures stay coherent or are resolved, impacting radiation patterns.

Contribution

It presents a novel method to dynamically decide colour coherence during jet-medium interactions in JEWEL, influencing jet quenching observables.

Findings

Suppression of hard radiation due to resolved colour dipoles.

Reduction in overall scattering rate from colour coherence effects.

Altered jet fragmentation and correlations consistent with coherence modifications.

Abstract

Colour coherence affects the radiation pattern of hard partons both in vacuum and in a dense coloured background formed in heavy ion collisions. In vacuum evolution it leads to the well-known phenomenon of angular ordering, and in heavy ion collisions the appearance of a medium resolution scale strongly affects the way in which a fragmenting hard parton interacts with the background medium. In this paper I present the implementation of colour coherence in the JEWEL event generator for jet evolution in a dense medium. In each interaction between a hard parton and the medium it is checked whether the momentum transfer of the scattering is sufficient to resolve the colour dipole. In this way it is dynamically decided which structures stay coherent. Importantly, scatterings that resolve an individual parton disrupt the colour coherence, which affects the next splitting via the loss of angular ordering. This leads to a suppression of hard radiation, and consequently a reduction in overall scattering rate, which is the dominant source of effects of colour coherence observable in reconstructed jets. I discuss these modifications using the examples of nuclear modification factor, jet fragmentation function and jet-hadron correlations.