Recent results and prospects on exploring the helicity structure of the proton at RHIC in high-energy polarized proton-proton collisions

The STAR Collaboration is pursuing measurements to help understand the origin of the proton spin. The gluon polarization is accesible via measurements of the longitudinal double-spin asymmetry, ALL , for inclusive charged and neutral pions and inclusive jet production. A recent global analysis of polarized DIS data and RHIC spin data disfavors extreme gluon polarization scenarios. The measurement of a parity violating single-spin asymmetry, AL, for W+(W−) bosons produced in longitudinally polarized p+p collisions at √ s = 500 GeV, is sensitive to helicity distribution functions for quarks and anti-quarks. The charge-sign reconstruction of charged leptons from W decays at forward rapidity requires an upgrade of the STAR tracking system based on a novel design of triple-GEM detectors.