Speaker
Description
The contribution to the spin of the proton from its constituents has been one of the unresolved questions in nuclear physics. The longitudinal spin program at STAR is exploring a wide range of measurements to determine the gluon helicity distribution inside the proton. The inclusive jets and pions in the kinematic range accessed by RHIC are dominated by quark-gluon and gluon-gluon scattering processes. The longitudinal double-spin asymmetry (ALL) is sensitive to polarized parton distributions and can be used to extract information about the gluon helicity contribution (∆G) to the spin of the proton. The 2009 STAR inclusive jet ALL measurements at √s = 200 GeV showed the first evidence of polarized gluons for gluon momentum fractions above 0.05. The data collected at √s = 510 GeV will extend the current constraints on ∆G to lower gluon momentum fractions, and the measurement of dijet ALL will allow for the reconstruction of the partonic kinematics at leading order. This presentation will focus on the recent results from the ALL measurements at STAR, and how they extend the sensitivity to the gluon spin contributions at lower momentum fractions.
