We present the first inclusive measurements of the invariant and softdrop jet mass in proton-proton collisions at $\sqrt{s}=200\mathrm{GeV}$ 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 nonperturbative 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.

• Received 24 March 2021
• Accepted 2 August 2021
• Corrected 1 October 2021

DOI:https://doi.org/10.1103/PhysRevD.104.052007

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Published by the American Physical Society