Transverse Single-Spin Asymmetry and Cross-Section for pi0 and eta Mesons at Large Feynman-x in Polarized p+p Collisions at sqrt(s)=200 GeV

TL;DR

This paper reports measurements of the cross-section and transverse single-spin asymmetry for pi0 and eta mesons at large Feynman-x in polarized proton-proton collisions at 200 GeV, providing insights into spin-momentum correlations.

Contribution

It presents the first measurements of A_N and cross-sections for pi0 and eta mesons at large x_F at forward rapidity in polarized p+p collisions at RHIC.

Findings

pi0 cross-section agrees with perturbative QCD predictions

eta/pi0 cross-section ratio matches previous measurements

eta asymmetry is significantly larger than pi0 asymmetry at high x_F

Abstract

Measurements of the differential cross-section and the transverse single-spin asymmetry, A_N, vs. x_F for pi0 and eta mesons are reported for 0.4 < x_F < 0.75 at an average pseudorapidity of 3.68. A data sample of approximately 6.3 pb^{-1} was analyzed, which was recorded during p+p collisions at sqrt{s} = 200 GeV by the STAR experiment at RHIC. The average transverse beam polarization was 56%. The cross-section for pi0 is consistent with a perturbative QCD prediction, and the eta/pi0 cross-section ratio agrees with previous mid-rapidity measurements. For 0.55 < x_F < 0.75, A_N for eta (0.210 +- 0.056) is 2.2 standard deviations larger than A_N for pi0 (0.081 +- 0.016).