Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized $p{+}p$ collisions at $\sqrt{s}=200$ GeV

TL;DR

This paper reports measurements of single-spin asymmetries for charged pions at midrapidity in transversely polarized proton-proton collisions at 200 GeV, finding results consistent with zero but hinting at possible flavor-dependent effects.

Contribution

First measurement of charged pion asymmetries at midrapidity in polarized proton collisions, exploring potential flavor dependence in spin asymmetry mechanisms.

Findings

Asymmetries are consistent with zero for individual charges.

Slight charge-dependent differences suggest flavor dependence.

Results align with neutral-pion asymmetries in the same kinematic range.

Abstract

In 2015, the PHENIX collaboration has measured single-spin asymmetries for charged pions in transversely polarized proton-proton collisions at the center of mass energy of $\sqrt{s}=200$ GeV. The pions were detected at central rapidities of $|\eta|<0.35$. The single-spin asymmetries are consistent with zero for each charge individually, as well as consistent with the previously published neutral-pion asymmetries in the same rapidity range. However, they show a slight indication of charge-dependent differences which may suggest a flavor dependence in the underlying mechanisms that create these asymmetries.