Data-driven extraction of the substructure of quark and gluon jets in proton-proton and heavy-ion collisions

TL;DR

This paper demonstrates a data-driven method using topic modeling and machine learning to separate quark and gluon jet contributions and analyze their substructures in proton-proton and heavy-ion collisions, aiding understanding of quark-gluon plasma effects.

Contribution

It introduces a novel, fully data-driven approach combining topic modeling and machine learning to extract quark and gluon jet substructures and their modifications in heavy-ion collisions.

Findings

Topic modeling effectively separates quark and gluon contributions.

Machine learning observables improve separation of jet types.

Results based on PYQUEN generator suggest experimental feasibility.

Abstract

The modification of quark- and gluon-initiated jets in the quark-gluon plasma produced in heavy-ion collisions is a long-standing question that has not yet received a definitive answer from experiments. In particular, the size of the modifications in the quark-gluon plasma differs between theoretical models. Therefore a fully data-driven technique is crucial for an unbiased extraction of the quark and gluon jet spectra and substructure. Corroborating past results, I demonstrate the capability of a fully data-driven technique called topic modeling in separating quark and gluon contributions to jet observables. The data-driven topic separation results can further be used to extract jet substructures, such as jet shapes and jet fragmentation function, and their respective QGP modifications. In addition, I propose the use of machine learning constructed observables and demonstrate the potential to increase separability for the input observable. This proof-of-concept study is based on proton-proton and heavy-ion collision events from the PYQUEN generator with statistics accessible in Run 4 of the Large Hadron Collider. These results suggest the potential for an experimental determination of quark- and gluon-jet spectra, their substructures, and their modification in the QGP.