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

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.