Measurement of Transverse Single-Spin Asymmetries for Mid-rapidity Production of Neutral Pions and Charged Hadrons in Polarized p+p Collisions at sqrt(s) = 200 GeV

TL;DR

This study measures transverse single-spin asymmetries for neutral pions and charged hadrons at mid-rapidity in polarized proton-proton collisions at 200 GeV, finding asymmetries consistent with zero and validating pQCD for cross section predictions.

Contribution

First measurement of transverse single-spin asymmetries at mid-rapidity in polarized p+p collisions at 200 GeV, providing new insights into spin effects in this kinematic region.

Findings

Asymmetries are consistent with zero within a few percent.

Inclusive charged hadron cross section agrees with NLO pQCD calculations.

pQCD successfully describes unpolarized cross sections above ~2 GeV/c.

Abstract

The transverse single-spin asymmetries of neutral pions and non-identified charged hadrons have been measured at mid-rapidity in polarized proton-proton collisions at sqrt(s) = 200 GeV. The data cover a transverse momentum (p_T) range 0.5-5.0 GeV/c for charged hadrons and 1.0-5.0 GeV/c for neutral pions, at a Feynman-x (x_F) value of approximately zero. The asymmetries seen in this previously unexplored kinematic region are consistent with zero within statistical errors of a few percent. In addition, the inclusive charged hadron cross section at mid-rapidity from 0.5 < p_T < 7.0 GeV/c is presented and compared to NLO pQCD calculations. Successful description of the unpolarized cross section above ~2 GeV/c using NLO pQCD suggests that pQCD is applicable in the interpretation of the asymmetry results in the relevant kinematic range.