Multi-dimensional measurements of parton shower in pp collisions at RHIC

Abstract

Jets, collimated sprays of hadrons, serve as an experimental tool for studying parton shower evolution. Differential measurements of jet substructure observables enable the exploration of perturbative and non-perturbative QCD processes. The SoftDrop grooming technique is based on removing soft wide-angle radiation and products of this procedure are substructure observables, such as the shared momentum fraction ($z_{\text{g}}$) and groomed jet radius ($R_{\text{g}}$). We present fully corrected correlations between the $z_{\text{g}}$ and $R_{\text{g}}$ at the first split for jets of varying momenta in $p$+$p$ collisions at the center of mass energy $\sqrt{s} = 200$ GeV. To study the evolution along the jet shower, we also present the $z_{\text{g}}$ and $R_{\text{g}}$ observables at the first, second, and third splits for various jet momenta. As these novel measurements are presented in three dimensions, we outline the correction procedure so that it can be used as a template for future multi-differential measurements across all experiments.