Single-spin asymmetries and invariant cross sections of the high transverse-momentum inclusiveπ0production in 200 GeV/cppandp¯pinteractions

The ${\mathrm{\pi }}^0$ 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 -0.15<${\mathit{x}}_{\mathit{F}}$<+0.15 and 1<${\mathit{p}}_{\mathit{T}}$<4.5 GeV/c. Improvements in the data analysis showed that our earlier large asymmetries at ${\mathit{p}}_{\mathit{T}}$≳3 GeV/c were not correct. These data indicate that PQCD expectations seem confirmed and the higher-twist contribution to the single-spin asymmetry in ${\mathrm{\pi }}^0$ production at ${\mathit{x}}_{\mathit{F}}$=0 is not large. Additional evidence for such a conclusion comes from the measurement of a semi-inclusive ${\mathrm{\pi }}^0$ asymmetry, where associated charged particles are detected opposite to the ${\mathrm{\pi }}^0$ azimuthal direction. This experiment also provides high-statistics data on the inclusive ${\mathrm{\pi }}^0$ cross sections for pp and p¯p collisions at √s≊19.4 GeV. © 1996 The American Physical Society.