Data on the multiplicity and inclusive spectra of γ produced in inelastic pNe20 and pN interactions at 300 GeV are presented. The γ multiplicity for pNe20 interactions is 11.43±0.23, and the ratio of 〈nγ〉 for pNe20 and pN interactions is 1.48±0.05. From an analysis of the effective-mass distributions, 〈nπ0〉=4.91±0.52 and 〈nη0〉=1.47±0.33. In fact, η0 production is much higher in pNe20 interactions [R(η0π0)=0.66±0.12 for np≥21] than in pN interactions [R(η0π0)=0.06±0.04]. No η′(958) signal is seen. Strong correlations between 〈nγ〉 and np, the number of secondary protons, are observed, primarily from the central and target fragmentation regions. Inclusive y* and p⊥ spectra are analyzed and evidence for low-energy cascading and rescattering of fast particles in the projectile fragmentation region is discussed. The data are compared to the predictions of the additive quark model, the Lund model, and the dual parton model.
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GAMMA-MULTIPLICITY FOR (PROTON-NUCLEON)-INTERACTION WAS OBTAINED AT AVERAGING OVER (PP) AND (PN) EVENTS, AND THEN WAS USED IN THE PRESENTED RATIO.
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The authors have measured the large-pT inclusive cross sections for π0 and η production near 90° in the center-of-mass system in 200-GeV/c π+ and proton collisions with beryllium, carbon, and aluminum targets. The cross section for both π0 and η mesons rises with increasing nucleon number (A) of the target nucleus as Aα, with α>1. The ratio of the π0 yield in pA collisions to that in π+A collisions decreases with increasing pT.
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THE CROSS SECTION HAS BEEN FITTED BY THE FORMULA: D(SIG)/D(PT**2)= CONST*EXP(-SLOPE*PT**2).
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Measurements of recognized π0 production in p-Be collisions for 0.1<X⊥<0.5 and −0.8<XF<0.0 at 200, 300, and 400 GeV/c are presented. These invariant cross sections are fitted by Edσdp3=A(1−XR)MP⊥−N over this range of X⊥ and XF with M=4.88±0.14 and N=8.90±0.10 independent of energy. No significant evidence for breaking of this scaling is observed over this large kinematic region at these energies.
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In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p–Be and p–Au collisions at 450 GeV/c at the CERN SPS. In the range covered up to ≈ 1.5 GeV/c2 the mass spectra from p–Be and p–Au collisions are well explained by electron pairs from decays of neutral mesons. For p–Au our result is new. For p–Be, the simultaneously measured electron pair inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/c2, and of 28% in the mass range above 750 MeV/c2 at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution.
Relative production cross sections.
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ALL NEGATIVE PARTICLES WAS CONSIDERED AS PI-.
ALL NEGATIVE PARTICLES WAS CONSIDERED AS PI-.
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