Inclusive jet cross section in $pp$ collisions at $\sqrt{s} = 200$ and $510$ GeV

TL;DR

This paper presents measurements of inclusive jet cross sections in proton-proton collisions at 200 and 510 GeV, providing data to better constrain the gluon parton distribution function and improve theoretical models.

Contribution

First measurements of inclusive jet cross sections at these energies that help refine gluon PDFs and tune QCD models.

Findings

Jet cross sections agree with NNLO QCD calculations within uncertainties.

Data extends the kinematic reach to low x values where gluon PDFs are poorly constrained.

Results will aid in tuning Monte Carlo generators and studying quark-gluon plasma.

Abstract

Jets are collimated clusters of particles formed by the hadronization of partons following a hard interaction. In proton-proton ($pp$) collisions at the Relativistic Heavy Ion Collider (RHIC), jet production is dominated by $gg$ and $qg$ partonic processes, allowing us to directly probe the gluon parton distribution function (PDF) in the proton in a way complementary to deep inelastic scattering. In this paper, we report the double-differential inclusive-jet cross sections as a function of jet transverse momentum, $p_{\rm T}$, and pseudorapidity, $\eta$, at center-of-mass energies $\sqrt{s} = 200$ and $510$~GeV, from $pp$ collisions studied with the STAR detector. The jet $p_{\rm T}$ is corrected for underlying event contributions by applying an off-axis cone method. At mid-pseudorapidity, $|\eta| < 0.9$, the kinematic coverage of our data extends to $0.07 < x_{\rm T} \text{ (}= 2p_{\rm T}{} / \sqrt{s} \text{)} < 0.5$ and $0.03 < x_{\rm T} < 0.31$ at $\sqrt{s} = 200$~and 510 GeV, respectively, where the gluon PDF is poorly constrained by the TeV-scale $pp$~($p\bar{p}$) colliders. The inclusive jet cross sections are compared to the next-to-next-to-leading order perturbative quantum chromodynamics calculations using several recent PDF sets as inputs. These results will further constrain the gluon PDF, help tune Monte Carlo generators, and provide critical reference data needed to study the quark-gluon plasma.