Probing Gluon Helicity with Dijets from $\sqrt{s}$ = 510 GeV Polarized Proton Collisions at STAR

Abstract

The production of jets in polarized proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering processes. The dijet longitudinal double-spin asymmetry $(A_{LL})$ is sensitive to the helicity distributions and may be used to extract information about the gluon helicity contribution $\Delta g(x,Q^2)$ to the spin of the proton. Previous STAR jet measurements at $\sqrt{s}$ = 200 GeV show evidence of polarized gluons for gluon momentum fractions above 0.05. The measurement of dijet $A_{LL}$ at $\sqrt{s}$ = 510 GeV will extend the current constraints on $\Delta g(x,Q^2)$ to lower gluon momentum fractions and allow for the reconstruction of the partonic kinematics at leading order. These proceedings present preliminary results from the dijet $A_{LL}$ measurement from $\sim 50p{b}^{-1}$ of $\sim 50\%$ polarized proton data taken during the 2012 RHIC run.