The 0 inclusive and semi-inclusive, single-spin asymmetries have been measured using transversely polarized, 200-GeV/c proton and antiproton beams colliding with an unpolarized hydrogen target. The measured asymmetries are consistent with zero within the experimental uncertainties for the kinematic region Ϫ0.15Ͻx F Ͻϩ0.15 and 1Ͻp T Ͻ4.5 GeV/c. Improvements in the data analysis showed that our earlier large asymmetries at p T Ͼ3 GeV/c were not correct. These data indicate that PQCD expectations seem confirmed and the higher-twist contribution to the single-spin asymmetry in 0 production at x F ϭ0 is not large. Additional evidence for such a conclusion comes from the measurement of a semi-inclusive 0 asymmetry, where associated charged particles are detected opposite to the 0 azimuthal direction. This experiment also provides high-statistics data on the inclusive 0 cross sections for pp and pp collisions at ͱsϷ19.4 GeV.
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