The π0 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<xF<+0.15 and 1<pT<4.5 GeV/c. Improvements in the data analysis showed that our earlier large asymmetries at pT≳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 π0 production at xF=0 is not large. Additional evidence for such a conclusion comes from the measurement of a semi-inclusive π0 asymmetry, where associated charged particles are detected opposite to the π0 azimuthal direction. This experiment also provides high-statistics data on the inclusive π0 cross sections for pp and p¯p collisions at √s≊19.4 GeV. © 1996 The American Physical Society.
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Pure inclusive reaction.
Semi-inclusive reaction where at least on associated charged particle is produced at (180+-30) degrees relative to the pi0.
Inclusive cross sections for the production of π ± and K ± mesons in proton-proton collisions have been measured at a c.m. energy √ s = 45 GeV, in the range 0.41 < x < 0.95 and 0.35 < p T < 1.45 GeV, where x = 2 p L/√ s and p L , p T are the longitudinal and transverse components of the momentum of the meson. Within the measured range the p T dependence of the invariant cross section is essentially independent of x and weakly dependent on the type of particle. For all particles the invariant cross sections at fixed p T fall by three orders of magnitude between x = 0.4 and 0.95. Except at the highest values of x and p T , the statistical accuracy is better than 10%. The data are compared with a triple-Regge model and with a simple quark-parton model.
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The properties of the diffractive peak observed in the mass spectra of systems recoiling against observed high-momentum protons emerging from pp collisions at the CERN ISR have been investigated. The cross sections in this peak have been found to have a steep t dependence which flattens out as | t | increases. The high mass side of the peak varies approximately as 1/ M 2 (where M is the missing mass of the recoiling system) and scales well in terms of the variable M 2 / s . The position of the maximum has been observed to move to lower values of M 2 / s as the kinematic boundary of this variable decreases with increasing s . The measured cross sections, integrated up to M 2 / s =0.05, rise by (15±5)% over the s range 549 to 1464 GeV 2 .
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