Single-spin asymmetries and invariant cross sections of the high transverse-momentum inclusive<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">π</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>production in 200 GeV/<i>c</i><i>pp</i>and<i>p¯p</i>interactions

The ${\mathrm{\ensuremath{\pi}}}^{0}$ 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 ${\mathit{p}}_{\mathit{T}}$\ensuremath{\gtrsim}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 ${\mathrm{\ensuremath{\pi}}}^{0}$ production at ${\mathit{x}}_{\mathit{F}}$=0 is not large. Additional evidence for such a conclusion comes from the measurement of a semi-inclusive ${\mathrm{\ensuremath{\pi}}}^{0}$ asymmetry, where associated charged particles are detected opposite to the ${\mathrm{\ensuremath{\pi}}}^{0}$ azimuthal direction. This experiment also provides high-statistics data on the inclusive ${\mathrm{\ensuremath{\pi}}}^{0}$ cross sections for pp and p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s\ensuremath{\approxeq}19.4 GeV. \textcopyright{} 1996 The American Physical Society.