Dimuon production is studied in 400-GeV proton-nucleus collisions. A strong enhancement is observed at 9.5 GeV mass in a sample of 9000 dimuon events with a mass $m_{\mu^+\mu^-} \to$ 5 GeV.
Two peaks were observed. Mass spectrum was fitted to one and two resonance hypothesis.
Neutron-proton differential cross sections have been measured with good statistics for four-momentum transfers 0.14<−t≲19.0 (GeV/c)2 at laboratory momenta ranging from 4.5 to 12.5 GeV/c. The experiment was carried out in a neutron beam at the Argonne National Laboratory zero-gradient synchrotron. These results in conjunction with previous n−p charge-exchange data provide almost complete elastic-scattering angular distributions in this momentum range.
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The mass spectrum of muon pairs in the range 5 to 15 GeV is studied in the inclusive reaction p+nucleus→μ++μ−+anything. The ϒ and continuum distribution are presented as is the A dependence of the continuum. Comparison with a parton-annihilation model yields a sea-quark distribution.
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We present proton-nucleus dimuon-production cross sections for masses between 4 and 15 GeV, center-of-mass rapidities between -0.23 and 0.6 and incident energies of 200, 300, and 400 GeV. The data confirm scaling to the 20% level. The dependence of continuum 〈pT〉 on beam energy is also presented.
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The production of the ϒ family in proton-nucleus collisions is clarified by a sixfold increase in statistics. Constraining ϒ,ϒ′ masses to those observed at DORIS we find the statistical significance of the ϒ′′ to be 11 standard deviations. The dependence of ϒ production on pt, y, and s is presented. Limits for other resonance production in the mass range 4-18 GeV are determined.
Cross section times branching ratio.
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BEBC filled in turn with hydrogen, and with a neon-hydrogen mixture, was exposed to the CERN SPS wide band neutrino and antineutrino beams. The ratios of the charged-current cross sections per nucleon, σ(νH 2 ) σ(ν Ne ) and σ( ν H 2 ) σ( ν Ne ) , between 20 and 300 GeV were found to be 0.656 ± 0.020 and 1.425 ± 0.052, respectively. Multiplying these ratios by the revised cross sections in neon, σ(ν Ne ) E = (0.723 ± 0.038) × 10 −38 cm 2 / GeV per nucleon and σ( ν Ne ) E = (0.351 ± 0.019) × 10 −38 cm 2 / GeV per nucleon, and their ratio, σ( ν Ne ) σ(ν Ne ) = 0.485 ± 0.020 ,, yields values for the total charged-current cross sections on protons, σ(νp)/ E and σ( ν p ) E , of (0.474 ± 0.029) × 10 −38 cm 2 /GeV and (0.500 ± 0.032) × 10 −38 cm 2 /GeV. respectively, and a value for the ratio σ( ν p ) σ(ν p ) of 1.053 ± 0.066.
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Nearly 40000 neutrino and antineutrino interactions in BEBC are compared to measure the differences between neon and deuterium in the quark and antiquark distributions and in the nucleon structure functions. The ratio of Ne to D cross sections indicates some decrease betweenx∼0.2 andx∼0.6. They distributions show there is no significant increase in the neon sea, but prefer a small decrease. Taken altogether, thex andy distributions and the measured total cross-sections indicate some change in the shape of the valence distributions. No significant dependence onA is observed for either the shape of the sea or the ratio of longitudinal to transverse cross-sections.
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An angular method of identifying diffractive excitation (DE) events for interactions of a hadron beam in nuclear emulsion is applied to identifying DE events in interactions of heavy ions beams. The ‘‘apparent’’ mean free paths (MFP) of DE processes for O16 (28Si) beams are 1.00±0.12, 2.4−0.7+1.6, and 2.2±0.4 (1.5±0.2) m, respectively, at 200, 60, and 14.6 GeV/nucleon, which corresponds to 20–10% of the MFP for total inelastic interactions. Distinctive features of diffractively excited nuclei are discussed.
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We present results on charm pair correlations measured in proton-emulsion interactions at s =38.7 GeV. The predictions of leading order QCD for the distributions in invariant mass, rapidity gap, x F , and polar angle in the charm pair CMS are qualitatively consistent with our measurements. The mean p T of the pairs is equal within errors to that measured in dilepton production at the same energy and mass range.
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We report results on D 0 and D + production in proton-emulsion interactions at s =38.7 GeV. A fit to the form (1−| x F |) n exp (−bp 2 T ) yields n=6.9 +1.9 −1.8 and b=0.84 +0.10 −0.08 (GeV/ c ) −2 . The total inclusive cross section, is assuming linear A dependence, is measured to be 38±3(stat.) ±13 (sys.) μ b for the D 0 and 38±9±14 μ b for the D + . A comparison of these results with previous measurements indicates that nuclear effects do not strongly influence charm production. The predictions of QCD are in good agreement with our data.
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail).
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