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

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.

Figures (2)

• Figure 1: Top panel: Invariant cross section vs. $p_T$ for the production of charged hadrons at mid-rapidity, averaged over sign. A 9.6% normalization uncertainty is not shown. The curve represents an NLO pQCD calculation at a renormalization scale of $p_T$Jager:2002xm. Middle panel: The relative statistical (points) and point-to-point systematic (band) errors. Bottom panel: The relative difference between the data and the theory with scales of $p_T$/2 (lower curve), $p_T$, and 2$p_T$ (upper curve).
• Figure 2: Mid-rapidity neutral pion and charged hadron transverse single-spin asymmetry, $A_N$, vs. transverse momentum. Points for positive hadrons have been shifted down by 50 MeV/$c$ to improve readability. The error bars indicate statistical uncertainties.