Quark and Gluon Jet Substructure

TL;DR

This study investigates the potential to distinguish quark-initiated jets from gluon-initiated jets at the LHC using simulation-based multivariate analysis, achieving high rejection rates and exploring various variables and methods.

Contribution

It provides a comprehensive simulation-based analysis of quark-gluon jet discrimination, evaluating multiple variables, generators, and techniques to improve event-by-event identification.

Findings

At 50% quark jet efficiency, 80-90% of gluon jets are rejected.

Combining multiple variables enhances discrimination performance.

Charged track analysis reduces pileup effects.

Abstract

Distinguishing quark-initiated jets from gluon-initiated jets has the potential to significantly improve the reach of many beyond-the-standard model searches at the Large Hadron Collider and to provide additional tests of QCD. To explore whether quark and gluon jets could possibly be distinguished on an event-by-event basis, we perform a comprehensive simulation-based study. We explore a variety of motivated and unmotivated variables with a semi-automated multivariate approach. General conclusions are that at 50% quark jet acceptance efficiency, around 80%-90% of gluon jets can be rejected. Some benefit is gained by combining variables. Different event generators are compared, as are the effects of using only charged tracks to avoid pileup. Additional information, including interactive distributions of most variables and their cut efficiencies, can be at http://jets.physics.harvard.edu/qvg.