Q-PYTHIA: a medium-modified implementation of final state radiation

TL;DR

Q-PYTHIA introduces medium-induced gluon radiation into PYTHIA, enabling realistic jet quenching simulations that account for medium effects on fragmentation, jet broadening, and energy loss, useful for heavy-ion collision analysis.

Contribution

It provides the first Monte Carlo implementation of medium effects in final state radiation within PYTHIA, incorporating medium-modified splitting functions for jet quenching studies.

Findings

Increased intra-jet multiplicities observed

Energy loss of leading particles demonstrated

Jet broadening effects confirmed

Abstract

We present a Monte Carlo implementation, within PYTHIA, of medium-induced gluon radiation in the final state branching process. Medium effects are introduced through an additive term in the splitting functions computed in the multiple-soft scattering approximation. The observable effects of this modification are studied for different quantities as fragmentation functions and the hump-backed plateau, and transverse momentum and angular distributions. The anticipated increase of intra-jet multiplicities, energy loss of the leading particle and jet broadening are observed as well as modifications of naive expectations based solely on analytical calculations. This shows the adequacy of a Monte Carlo simulator for jet analyses. Effects of hadronization are found to wash out medium effects in the soft region, while the main features remain. To show the performance of the implementation and the feasibility of our approach in realistic experimental situations we provide some examples: fragmentation functions, nuclear suppression factors, jet shapes and jet multiplicities. The package containing the modified routines is available for public use. This code, which is not an official PYTHIA release, is called Q-PYTHIA. We also include a short manual to perform the simulations of jet quenching.