Measurement of the cross section and longitudinal double-spin asymmetry for di-jet production in polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV

TL;DR

This paper presents the first measurement of the double-spin asymmetry in di-jet production in polarized proton-proton collisions at 200 GeV, supporting positive gluon polarization in the proton.

Contribution

It provides the first experimental data on $A_{LL}$ for di-jet production at this energy, testing and supporting recent NLO global analyses of gluon polarization.

Findings

Measured di-jet cross section agrees with NLO pQCD predictions.

Measured $A_{LL}$ supports positive gluon polarization around 0.2 for $x > 0.05$.

Results are consistent across different jet topologies.

Abstract

We report the first measurement of the longitudinal double-spin asymmetry $A_{LL}$ for mid-rapidity di-jet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s} = 200$ GeV. The di-jet cross section was measured and is shown to be consistent with next-to-leading order (NLO) perturbative QCD predictions. $A_{LL}$ results are presented for two distinct topologies, defined by the jet pseudorapidities, and are compared to predictions from several recent NLO global analyses. The measured asymmetries, the first such correlation measurements, support those analyses that find positive gluon polarization at the level of roughly 0.2 over the region of Bjorken-$x > 0.05$.