The azimuthal correlation distribution of 102 charmed-particle pairs observed in the hybrid emulsion experiment WA75 is compared with theoretical predictions. The various pairs - (D − D 0 ), (D − D + ), (D 0 D 0 ) and (D + D 0 )-all s how, within statistical error, the same azimuthal correlation distribution, demonstrating its independence from the specific nature of the production channel. Among the decays of 150 charged charmed particles and 138 neutral ones seen, higher multiplicities are favoured for hadronic as opposed to semileptonic decays. The data are consistent with the muonic decays of charged D mesons proceeding through the channels (μ ± , v, K 0 ) and [μ ± , v, K ∗0 (892)] , the fraction through K 0 being 0.76±0.06.
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Two-jet mass distributions have been measured as a function of centre-of-mass scattering angle for high-mass jet pairs produced in proton-antiproton collisions at the CERN collider operating at a centre-of-mass energy of 630 GeV. The agreement between QCD expectations and the experimental measurements has been used to place limits on the production cross section of an object X decaying into two jets. In particular we consider the existence of a massive colour octet of vector gauge bosons (axigluons). We exclude axigluons with a width Λ A < 0.4 m A and a mass m A in the range 150 < m A < 310 GeV/ c 2 (95% CL).
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Isolated photons, produced directly by a scattering process, have been observed in the UA1 experiment at the CERN p p collider at centre-of-mass energies √=546 GeV and √=630 GeV . Single and double photon differential cross sections have been determined and found to be consistent with the expectations of QCD.
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A search for single photons, produced in e + e − collisions together with particles interacting only weakly with matter, has been performed using the CELLO detector at the PETRA storage ring. We report on results from data taken at 35 GeV < √ s <46.57 GeV. An upper limit of 8.7 (90% CL) on the number of light neutrino species is set. Combining our result with published results from other e + e − experiments the number of light neutrinos is limited to N v < 4.6 at 90% CL. We also set lower limits on the masses of supersymmetric particles.
TWO RUN AT DIFFERENT ENERGIES COMBINED, 1.26 EVENTS WAS FOUND.
The production of transverse energy clusters in minimum bias proton-antiproton collisions at the CERN SPS Collider is studied with the UA1 detector over a new range of centre of mass energies (√ s = 0.2−0.9 TeV). This study is intended to investigate how low in transverse momentum perturbative QCD is able to describe the dynamics of hadron collisions. We observe that clusters with transverse energy in excess of a few GeV exhibit properties in agreement with QCD expectations for parton scattering, supporting their interpretation in terms of jet production. We find that the jet-event rate represents a sizeable fraction of the inelastic rate and is increasing with √ s over the measured energy range.
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The inclusive yield of photons has been measured from deep inelastic interactions of 200 GeV muons on hydrogen. After subtracting the contributions from hadron electromagnetic decays and Bethe-Heitler muon bremsstrahlung, residual photons are observed at low p T and low z at a mean level of 0.15±0.06 per interaction. The quark Compton scattering process is unable to explain the data, thus indicating an anomalous photon production.
Z distribution of anomalous direct photons.
PT distribution of anomalous direct photons.
Using the Crystal Ball detector operating at the DORIS II storage ring we have measured the leptonic partial widthsГeeof the Υ(1S) and Υ(2S) reson
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η production has been investigated by the Mark II collaboration at the SLAC e+e− storage ring PEP. η particles are reconstructed by their γγ decay mode. The η fragmentation function has been measured and found to be in good agreement with the Lund-model prediction. η′ production has been measured for the first time in high-energy e+e− annihilation. There is evidence at the 3σ level for Ds± decay into ηπ± and η′π±.
Numerical values supplied by G.Wormser.
Z = 0.0 point extrapolated using LUND fragmentation model.
Z = 0.0 point extrapolated using LUND fragmentation model.
This paper reports studies of the reactions γp→ρ π π πp and γp→ρ ρ πp. In particular a peak is reported in the ρ ρ π mass spectrum with closely similar mass and width to those of the ω ρ π peak previously reported in the reaction γp→ω ρ πp. The ratio of production cross sections is found to be ρ ρ π/ω ρ π=0.96±0.19, in serious disagreement with the expectation from Vector Meson Dominance. A possible explanation is indicated.
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Numerical values requested from authors.
We report the first direct observation of B meson decays into Λ c + baryons using the decay channel Λ c + → pK − π + . The product of branching ratios Br(B→Λ c + X)·Br(Λ c + →pK − π + = (0.30±0.12±0.06)% is derived from an observed signal of 208±89 events. Using previous measurements of inclusive baryon rates we find a branching ratio for Λ c + → pK − π + of (4.1±2.4)%. The measured Λ c + momentum spectrum indicates that the multi-particle final states dominate the decay B→Λ c + X.
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