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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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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We have measured neutral and charged current interactions of ν μ and ν μ on proton and neutron. From a combination of ratios we determine the neutral current chiral coupling constants. The results are u 2 L = 0.13 ± 0.03, d 2 L = 0.19 ± 0.03, u 2 R = 0.02 ± 0.02 and d 2 R = 0.00 ± 0.02. These results agree with the predictions of the standard SU(2) × U(1) model. The corresponding value of sin 2 θ W is 0.20 ± 0.04.
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Results on moments of the azimuthal angle ϕ of final state hadrons from 120 GeV and 280 GeV μp scattering are presented. A ϕ asymmetry is observed and its W 2 , Q 2 , z and p T dependences compared with model calculations which include intrinsic transverse momentum and first order QCD corrections. These studies indicate that the observed asymmetry is mainly due to intrinsic transverse momentum k T .
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Typical phi distribution.
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Thez andpT2 distributions of π0 mesons produced by the interaction of 200 GeV muons on hydrogen are presented. Comparisons are made with other π0 and charged hadron data and with the predictions of perturbative QCD. The data show a rise of 〈pT2〉 withW2 which is consistent with QCD, and withz2 which requires a contribution from a primordialkT. The fraction of total energy which appears as π0 mesons is 0.27±0.05.
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The deuteron structure function F 2 d has been measured in 280 GeV μ + d interactions. Existing measurements of F 2 p , made with the same apparatus, are used to calculate F 2 p − F 2 n and F 2 n F 2 p . The ratio F 2 n F 2 p has a similar x dependence to that of earlier measurements at lower Q 2 .
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Using the data on deep inelastic muon scattering on iron and deuterium the ratio of the nucleon structure functions F 2 N ( Fe )/ F 2 N ( D ) is presented. The observed x -dependence of this ratio is in disagreement with existing theoretical predictions.
RANGE OF Q*2 VARIES WITH X. E.G. AT X=0.05 , 9<Q2<27. AT X=0.65 , 36<Q2<170 GEV**2.
About 2000 neutral induced interactions observed inside the hydrogen filled TST in BEBC have been analysed. The data were obtained from an exposure to the v μ wide band beam at the CERN SPS. A separation of these events into charged current, neutral current and neutral hadron induced interactions have been achieved using a multidimensional kinematic analysis. The neutral to charged current cross section ratio for v μ interactions on free protons has been determined avoiding the drastic cuts on the data inherent in previous experiments. The result R P v = 0.47 ± 0.04 is compatible with those measurements and the prediction of the standard SU (2) × U (1) model for sin 2 θ W = 0.18 ± 0.04.
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The ratios of neutral current to charged current cross sections of neutrino and antineutrino interactions in heavy Ne/H 2 mixture have been measured in BEBC. The beam was the CERN SPS 200 GeV/ c narrow band beam. The ratios were obtained using a cut in the transverse momentum of the hadronic system. In the standard Glashow-Salam-Weinberg model, our results correspond to the value of sin 2 θ w = 0.182 ± 0.020 ± 0.012. By combining this experiment with data from a hydrogen target the coupling constants u L 2 and L 2 are found to be 0.15 ± 0.04 and 0.19 ± 0.05, respectively.
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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.
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