Cross Sections and Transverse Single-Spin Asymmetries in Forward Neutral-Pion Production from Proton Collisions at \sqrt{s} = 200 GeV

TL;DR

This paper reports measurements of forward neutral-pion production in polarized proton collisions at 200 GeV, showing cross sections consistent with QCD and revealing spin asymmetries that increase with Feynman x, aligning with theoretical models.

Contribution

First significant measurement of transverse single-spin asymmetries for high-pT neutral pions at a polarized proton collider, confirming QCD predictions.

Findings

Cross section agrees with next-to-leading order perturbative QCD.

Analyzing power is small at low x_F and large at high x_F.

Results support perturbative QCD model expectations.

Abstract

Measurements of the production of forward high-energy pi0 mesons from transversely polarized proton collisions at \sqrt{s}=200 GeV are reported. The cross section is generally consistent with next-to-leading order perturbative QCD calculations. The analyzing power is small at x_F below about 0.3, and becomes positive and large at higher x_F, similar to the trend in data at \sqrt{s}<=20 GeV. The analyzing power is in qualitative agreement with perturbative QCD model expectations. This is the first significant spin result seen for particles produced with p_T>1 GeV/c at a polarized proton collider.