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 $\sim50 pb^{-1}$ of $\sim50 \%$ polarized proton data taken during the 2012 RHIC run.