Forward Neutral Pion Transverse Single Spin Asymmetries in p+p Collisions at \sqrt{s}=200 GeV

TL;DR

This paper presents detailed measurements of transverse single spin asymmetries in neutral pion production from polarized proton collisions at 200 GeV, testing QCD models and revealing discrepancies in p_T dependence.

Contribution

It provides the first measurements of p_T dependence of asymmetries and compares x_F and p_T dependencies with perturbative QCD predictions.

Findings

x_F dependence aligns with pQCD models

p_T dependence results are inconsistent with pQCD calculations

First measurements of transverse momentum dependence of asymmetries

Abstract

We report precision measurements of the Feynman-x dependence, and first measurements of the transverse momentum dependence, of transverse single spin asymmetries for the production of \pi^0 mesons from polarized proton collisions at \sqrt{s}=200 GeV. The x_F dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks and gluons within the proton as the origin of the spin effects. Results for the p_T dependence at fixed x_F are not consistent with pQCD-based calculations.