Measurements of single transverse spin asymmetries for hadron productions in s = 200 GeV p+p collisions at STAR

Abstract

The question of how the spin degrees of freedom in the nucleon are organized has not yet been fully answered. Forward hadron production in transversely polarized p+p collisions provides a unique way of probing the spin structure of the nucleon. Large (10% or more) single transverse spin asymmetries (AN) were measured at a wide range of collision energy. The STAR collaboration has previously measured π0 production with the Forward Pion Detector (FPD) at RHIC, and reported that large AN persists up to s = 200 GeV. A Pb‐glass electromagnetic calorimeter detector named the Forward Meson Spectrometer (FMS) has been built and installed at STAR. The FMS covers the pseudo‐rapidity region of 2.5<η<4.2 and the full azimuth. The FMS’s large acceptance allows us to extend measurements to higher pT, to heavier mass regions, and to multi particle final states. STAR has collected data with the FMS during Run 8. Results of AN measurements using the FMS and FPD will be presented.