Theory of hard probes in PbPb collisions

TL;DR

This paper reviews recent theoretical advances in understanding jet substructure modifications in quark-gluon plasma created in PbPb collisions, emphasizing effective field theory techniques and comparison with LHC data.

Contribution

It introduces new effective field theory calculations of jet shapes and cross sections in heavy ion collisions, advancing the precision of jet quenching studies.

Findings

Good agreement between theoretical calculations and LHC measurements

Jet substructure observables effectively probe medium properties

Systematic resummation improves calculation accuracy

Abstract

The jet quenching phenomenon in heavy ion collisions provides a strong evidence of the modification of parton shower in the quark-gluon plasma. This contribution focuses on the hard probes of QGP using jets and summarizes the new theoretical progress of jet substructure modification studies using effective field theory techniques. We emphasize the important role of jet substructure observables as they probe various aspects of the jet formation mechanism and allow us to study the medium properties in great details. The precise calculations require the systematic resummation and consistently including medium modifications. Specifically, we discuss the calculations of jet shapes and cross sections in proton-proton and lead-lead collisions at the LHC using soft-collinear effective theory, with Glauber gluon interactions in the medium. In the end we present the comparison between our calculations and the recent measurements at the LHC with very good agreement. We conclude that precise jet modification studies in heavy ion collisions has been initiated.