YaJEM - a Monte Carlo code for in-medium shower evolution

TL;DR

YaJEM is a Monte Carlo simulation tool designed to model in-medium parton shower evolution in heavy-ion collisions, aiding in understanding jet quenching and medium effects on reconstructed jets at high energies.

Contribution

This paper introduces the YaJEM Monte Carlo code for simulating in-medium jet evolution, providing a new tool to study jet quenching phenomena.

Findings

YaJEM successfully models medium-modified parton showers.

The code helps interpret jet quenching measurements.

It offers a framework to test approximations in jet-medium interaction models.

Abstract

High transverse momentum (P_T) QCD scattering processes are regarded as a valuable tool to study the medium produced in heavy-ion collisions, as due to uncertainty arguments their cross section should be calculable independent of medium properties whereas the medium then modifies only the final state partons emerging from a hard vertex. With the heavy-ion physics program at the CERN LHC imminent, the attention of high P_T physics in heavy ion collisions is shifting from the observation of hard single hadrons to fully reconstructed jets. However, the presence of a background medium at low P_T complicates jet-finding as compared to p-p collisions. Monte-Carlo (MC) codes designed to simulate the evolution of parton showers evolving into hadron jets are valuable tools to understand the complicated interplay between the medium modification of the jet and the bias introduced by a specific jet-finding scheme. However, such codes also use a set of approximations which needs to be tested against the better understood single high P_T hadron observables. In this paper, I review the ideas underlying the MC code YaJEM (Yet another Jet Energy-loss Model) and present some of the results obtained with the code.