Spin effects in large rapidity neutral pion production at STAR

Abstract

First measurements of large Feynman x (x_F) neutral pion production in polarized proton collisions at sqrt(s)=200 GeV were reported previously. Cross section measurements at <eta>=3.3 and 3.8$ and analyzing power (A_N) measurements at <eta>=3.8 were completed for 0.3 < x_F < 0.6. The cross section was found to be consistent with next-to-leading order perturbative QCD calculations. In that framework, the dominant subprocess is partonic collisions of valence quarks on low Bjorken-x gluons. The A_N was found to be large and positive and increasing with x_F, and consistent with phenomonological calculations based on the Collins effect, the Sivers effect and initial-state and final-state higher twist contributions. Subsequent data have been acquired with transverse polarized proton collisions at RHIC at sqrt(s)=200 GeV. The status of the analysis and preliminary results will be presented.