Single-Spin Asymmetries in Inclusive Charged Pion Production by Transversely Polarized Antiprotons

The analyzing power AN in inclusive π^- and π⁺ production has been measured with a 200 GeV/c transversely polarized antiproton beam over a wide xF range (0.2≤xF≤0.9) and at moderate pT (0.2≤pT≤1.5GeV/c). The asymmetry AN increases with increasing xF from zero to large positive values for π^-'s, and decreases from zero to large negative values for π⁺'s. A threshold for the onset of the asymmetry is observed about pT~0.5GeV/c, below which AN is essentially zero and above which AN increases (decreases) with pT for π^-'s ( π⁺'s) in the covered pT range.