Single-Spin Asymmetry of Inclusive π~0-Meson Production in 40-GeV Pion Interactions with a Polarized Target in the Target-Fragmentation Region

摘要

Data on the single-spin asymmetry (A_N) of inclusive π~0 production in 40-GeV pion interactions with a polarized target, π~- + p↑ → π~0 + X, are presented for the target-fragmentation region. The result is A_N = (-13.8 ± 3.8)% for -0.8 < x_F < -0.4 and 1 < pT < 2 GeV/c and is compatible with zero for -0.4 < x_F < -0.1 and 0.5 < pT < 1.5 GeV/c. At a π~0 momentum of about 1.7 GeV/c in the c.m. frame, the asymmetry becomes nonzero both in the central and in the target-fragmentation region. The behavior of the asymmetry is similar to that observed in the beam-fragmentation region of the E-704 (FNAL, 200 GeV) and STAR (BNL, 20 TeV) experiments, which employed a polarized proton beam.