Tagging the initial state gluon in the Z+jet process

TL;DR

This paper introduces a theoretically robust jet flavour tagging method using jet angularities to identify initial-state gluons in Z+jet events, potentially aiding gluon PDF determination.

Contribution

It develops an IRC-safe jet flavour tagger based on jet angularities, incorporating recent calculations to improve gluon tagging in electroweak boson plus jets processes.

Findings

Jet angularities exhibit Casimir Scaling at LL accuracy.

Tagging the leading jet enhances initial-state gluon purity.

Transverse momentum distributions can probe gluonic structure.

Abstract

We develop a jet flavour tagger in the contest of electroweak boson production in association with jets. Here the jet with the highest transverse momentum is considered and a simple cut on a jet angularity may serve as a tagger for the flavour of the jet. This is an infrared and collinear (IRC) safe procedure thus it is well-defined from a theoretical viewpoint. Jet angularities exibit a property called Casimir Scaling (CS) at the leading logarithmic (LL) accuracy. Here we consider also the first deviation from the typical CS behaviour because we use the most recent jet angularities calculations. Tagging the leading jet as quark-initiated permits us to enhance the initial-state gluon purity. We will consider transverse momentum distributions for tagged and no-tagged jets, with and without grooming. They could be potentially interesting observables to probe gluonic degrees of freedom of the colliding protons. In particular it may be worth to investigate if such a study might be a new handle on the determination of the gluon parton distribution function (PDF).