Invariant Jet Mass Measurements in $pp$ Collisions at $\sqrt{s} = 200$ GeV at RHIC

TL;DR

This paper reports the first measurements of invariant and SoftDrop jet mass in proton-proton collisions at 200 GeV at RHIC, comparing results with Monte Carlo simulations and perturbative QCD to improve understanding of jet structure.

Contribution

It provides the first inclusive measurements of jet mass at RHIC energies, fully corrected for detector effects, and compares them with various Monte Carlo models and theoretical calculations.

Findings

STAR-tuned PYTHIA-6 reproduces the data

LHC tunes of PYTHIA-8 and HERWIG-7 do not agree with the data

SoftDrop grooming aligns jet mass distributions closer to partonic predictions

Abstract

We present the first inclusive measurements of the invariant and SoftDrop jet mass in proton-proton collisions at $\sqrt{s}=200$ GeV at STAR. The measurements are fully corrected for detector effects, and reported differentially in both the jet transverse momentum and jet radius parameter. We compare the measurements to established leading-order Monte Carlo event generators and find that STAR-tuned PYTHIA-6 reproduces the data, while LHC tunes of PYTHIA-8 and HERWIG-7 do not agree with the data, providing further constraints on parameter tuning. Finally, we observe that SoftDrop grooming, for which the contribution of wide-angle non-perturbative radiation is suppressed, shifts the jet mass distributions into closer agreement with the partonic jet mass as determined by both PYTHIA-8 and a next-to-leading-logarithmic accuracy perturbative QCD calculation. These measurements complement recent LHC measurements in a different kinematic region, as well as establish a baseline for future jet mass measurements in heavy-ion collisions at RHIC.