Pure Quark and Gluon Observables in Collinear Drop

TL;DR

This paper introduces a new class of observables in jet physics that are purely sensitive to quarks or gluons, constructed through linear combinations of jet mass distributions using the collinear drop technique, validated by theoretical and simulation analyses.

Contribution

It presents a novel method to isolate pure quark or gluon observables using collinear drop grooming, with perturbative predictions and nonperturbative shape function modeling.

Findings

Observables are effective in both perturbative and nonperturbative regions.

The construction is validated with NLL resummation and Monte Carlo simulations.

Parameter choices are optimized for experimental application.

Abstract

We construct a class of pure quark and gluon observables by using the collinear drop grooming technique. The construction is based on linear combinations of multiple cumulative distributions of the jet mass in collinear drop, whose specific weights are fully predicted perturbatively. This yields observables which obtain their values purely from quarks (or purely from gluons) in a wide region of phase space. We demonstrate this by showing that these observables are effective in two phase space regions, one dominated by perturbative resummation and one dominated by nonperturbative effects. The nonperturbative effects are included using shape functions which only appear as a common factor in the linear combinations constructed. We test this construction using a numerical analysis with next-to-leading logarithmic resummation and various shape function models, as well as analyzing these observables with Pythia and Vincia. Choices for the collinear drop parameters are optimized for experimental use.