A theory of jet shapes and cross sections: from hadrons to nuclei

TL;DR

This paper develops a theoretical framework for analyzing jet shapes and cross sections in heavy ion collisions at the LHC, enabling detailed tests of QCD and medium effects in quark-gluon plasma environments.

Contribution

It introduces a novel approach to simulate and interpret jet modifications in QGP, linking gluon emission patterns with jet quenching and broadening.

Findings

Jet shape and cross section measurements can test QCD in high-energy heavy ion collisions.

Stimulated gluon emission correlates with jet quenching patterns.

Minimal increase in mean jet radius despite large jet attenuation.

Abstract

For jets, with great power comes great opportunity. The unprecedented center of mass energies available at the LHC open new windows on the QGP: we demonstrate that jet shape and jet cross section measurements become feasible as a new, differential and accurate test of the underlying QCD theory. We present a first step in understanding these shapes and cross sections in heavy ion reactions. Our approach allows for detailed simulations of the experimental acceptance/cuts that help isolate jets in such high-multiplicity environment. It is demonstrated for the first time that the pattern of stimulated gluon emission can be correlated with a variable quenching of the jet rates and provide an approximately model-independent approach to determining the characteristics of the medium-induced bremsstrahlung spectrum. Surprisingly, in realistic simulations of parton propagation through the QGP we find a minimal increase in the mean jet radius even for large jet attenuation. Jet broadening is manifest in the tails of the energy distribution away from the jet axis and its quantification requires high statistics measurements that will be possible at the LHC.