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

The analyzing power A_N in inclusive π^- and π⁺ production has been measured with a 200 GeV/c transversely polarized antiproton beam over a wide x_F range \(0.2<=x_F<=0.9\) and at moderate p_T \(0.2<=p_T<=1.5 GeV/c\). The asymmetry A_N increases with increasing x_F 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 p_T~0.5 GeV/c, below which A_N is essentially zero and above which A_N increases (decreases) with p_T for π^-'s ( π⁺'s) in the covered p_T range.