Inclusive cross sections and invariant single-particle distributions are presented for positive pions and protons produced in 8.05-GeV/c π−p and 18.5-GeV/c π±p inclusive reactions. Distributions in pT2 and in the longitudinal variables x, y (c.m.) and pl (lab) are shown. Comparisons are made with inclusive distributions for other particles produced in the same reactions.
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We have studied muon-produced hadrons from a deuterium target. The structure functions and the charge ratios are reported for neutrons; the transverse momentum and azimuthal distributions are reported for deuterons. The structure function for the neutron is similar to that of the proton. The charge ratio of produced hadrons follows the expectation of a simple spin-½ quark model. Transverse-momentum results agree with those at lower energy and are similar to those from hadron-hadron interactions. No azimuthal anisotropy is seen.
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Inclusive and semi-inclusive cross sections for gp0 production in 100, 200, and 360 GeV/c π−p interactions are presented. Differential cross sections for ρ0 production as functions of c.m. rapidity and transverse momentum are compared with the corresponding differential cross sections for pion production. Effects of various methods of estimating background on the values obtained for ρ0 production cross sections are discussed. About 10% of the final-state charged pions appear to come from ρ0 decay. Thus, while ρ0 production and decay is a significant source of final-state pions, other sources must contribute the majority of the produced pions.
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The final states of charged hadrons produced in 280 GeV μp scattering are analysed with respect to their planarity and jet structure. Distributions of p ⊥ 2 in and p ⊥ out 2 are presented. A two jet structure in the forward hemisphere is observed for events with high p ⊥ tracks are predicted by QCD models.
PTIN**2 is the sum of the PTIN components squared.
PTOUT**2 is the sum of the PTOUT components squared.
The production of J/ ϑ and ϑ′ has been measured in 250 GeV muon iron interactions. The measured total cross sections are σ ( μ N → μ J/ ϑ X)=0.74±0.14 nb and σ ( μ N → μϑ ′X)=0.16 ± 0.07 nb. An upper limit on the cross section times branching ratio for ϒ production of BR · σ ( μ N → μϒ X) < 5.2 × 10 −38 cm 2 (at 90% confidence level) is obtained. About half the J/ ϑ cross section is found to have Z ⩾ 0.95 (where Z = E (J/ ϑ / ν ). The first-order photon-gluon fusion model agrees well with the measured Q 2 and ν dependence of the J/ ϑ data and is used to extract the gluon momentum distribution. However, higher order QCD effects are needed to explain the Z distribution of the J/ ϑ and the observed broadening of the P t 2 distribution with decreasing Z . The decay angular distributions of the J/ ϑ are found to be flat in the s -channel frame, but there is evidence for polarisation in the t -channel frame.
NUMBERS ARE CROSS-SECTIONS FOR PSI AND PSI(PRIME) BUT CROSS-SECTION*BR.RATIO FOR THE UPSILON.
THE COHERENT PRODUCTION IS NOT SUBTRACTED.
THE COHERENT PRODUCTION IS SUBTRACTED.
Dimuon and trimuon events produced by the interaction of 250 GeV muons in an iron target have been studied and are shown to originate predominantly from charm production. The data are used to measure the contribution of charm to the nucleon structure function F 2 . The cross sections for real photoproduction ( Q 2 =0) of charm in the current fragmentation region are derived as a function of photon energy and are found to be ∼0.6% of the total, hadronic photoproduction cross section in this energy range. The measured cross sections are found to be well represented by the photon-gluon fusion model. The charmed quark fragmentation function is obtained by using this model to fit the measured decay muon energy distribution and is found to be well represented by exp(1.6±1.6) Z . The data are used to study the momentum distribution of the gluons in the nucleon. An upper limit of 1.4% (90% confidence level) is set on the branching ratio D→ μν and a model-dependent upper limit on the branching ratio F→ μν is derived.
The charm contribution to the nucleon structure function from the dimuon data.
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Identification of muons in hadronic events from e+e− annihilation observed in the MAC detector at the storage ring PEP provides flavor tagging of heavy primary quarks. A sample enriched in events from bb¯ production is obtained and the b-quark fragmentation function is inferred from the momentum spectrum of the muons. The b quark is found to fragment predominantly with high values of z, with 〈zb〉=0.8±0.1, and to have an over-all semimuonic branching fraction of (15.5−2.9+5.4)%.
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We have studied inclusive production of KS0, Λ, and Λ¯ particles in 20-GeV γp interactions and have found features similar to those observed in both hadronic and leptonic interactions. The production cross sections, charged-particle multiplicities, and average Λ polarization are reported. Inclusive distributions of x and pT are shown and discussed in terms of quark fragmentation models. Production cross sections for K*(890) and Σ*(1385) are also reported.
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Inclusive ϱ 0 meson production has been measured in 120 GeV and 280 GeV muon-proton interactions. Distributions of z and p T 2 are presented. Primary ϱ 0 production is found to be equal to that of π 0 production within errors.
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New results on the forward produced protons and antiprotons in high energy muon-nucleon scattering are presented. Their W 2 , z and p 2 T dependences are compared with those of the other charged hadrons. Significant differences are observed which can be related to the flavour content of the target and to a difference between the baryon content of quark and gluon jets.
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