We present a study of\(B\bar B\) meson pair production inπ− interactions at 140, 194 and 286 GeV incident pion energy. At 286 GeV, where we have the best statistics, we find a model-dependent\(B\bar B\) production cross-section\(\sigma _{BB}= 14_{ - 6}^{ + 7} nb/nucleon\).
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We present the final results from the search for μe pairs produced in neutrino interactions using the freon filled bubble chamber SKAT. The rate of μ−e+ pairs to charged current events above the charm threshold is\(R_{\mu ^ -e^ +}= (4.8 \pm 1.1)10^{ - 3} \). Assuming charm particle production to be the origin of the positron we calculate\(R_{\Lambda _c^ +}= (6.2 \pm 3.1)10^{ - 2} \) andRD=(2.8±0.9)10−2. We observe no considerable μ−e− pair production above the background. In the regionEv>3 GeV,pμ,e>1.0 GeV/c andpμ>pe we find with a 90% confidence level the limit\(R_{\mu ^ -e^ -}< 1.7 10^{ - 4} \).
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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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The inclusive production of Ks0, Λ, Λ¯, and Ks0Λ in the p¯Ta reaction at 4 GeV/c was measured and compared with that in the p¯p reaction. The total inelastic and topological cross sections were also measured. The number of Λ’s produced in the p¯Ta reaction was 11.3 times larger than that expected from the geometrical cross section, which is defined as A2/3 times the cross section for the p¯p reaction. The yield ratio Λ¯/Λ was found to be 2×10−2. These values cannot be accounted for by a straightforward extension of the p¯N reaction. Besides, a correlation of 2 vees like Ks0-Λ could not prove their simultaneous production. Nuclear temperatures of 135 and 97 MeV were obtained from the kinetic energy spectra of Ks0 and Λ, respectively. The kinematical characteristics of the Ks0 and Λ produced were analyzed in terms of the fireball model.
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The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the dimuon massM and transverse momentumPT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at highET)/(ψ/Continuum at lowET), from which theJ/ψ relative suppression can be extracted. This suppression is enhanced at lowPT.
Ratio of number of J/PSI's to number of continuum events in given mass interval.
We measured the differences in R=σLσT and the cross-section ratio σAσD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤5 (Gev/c)2. Our results for RA−RD are consistent with zero for all x and Q2, indicating that possible contributions to R from nuclear higher-twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q2, are now in agreement.
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Inclusive ψ production in e+e− annihilation at 29 GeV has been measured with the Mark II detector. The ψ cross section is found to be 1.1±0.5±0.4 pb. After subtraction of the expected contribution from B decay, an upper limit of 0.02σμμ is obtained for other sources of ψ production.
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We have found 122 charmed-particle decays among 3855 neutrino interactions located in the fiducial volume of a hybrid emulsion spectrometer installed in the Fermilab wide-band neutrino beam. We obtain an average relative charmed-particle production cross section of σ(ν μ → c μ − ) σ(ν μ →μ − ) =4.9 −0.6 +0.7 % , at an average neutrino energy of 22 GeV. We also obtain a production rate of σ(ν μ → c c ν μ ) σ(ν μ →ν μ ) =0.13 −0.11 +0.31 % , if we assume that there was an undetected muon, a limit of σ(ν μ → c c μ − ) σ(ν μ → c μ − )<3% (90% CL ) can be obtained. Other cross section ratios and limits are also presented.
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High statistics data of the ηππ system in π − p → ηπ + π − n were obtained. A partial wave analysis was performed in the mass region between 1.37 and 1.85 GeV. Resonant structures were observed in the IJ PC = 11 −− wave around 1.6 GeV and in 13 −− around 1.7 GeV. The structure in 11 −− was fitted with a single Breit-Wigner and also fitted with two Breit-Wigner's. The result suggests the possible existence of two vector resonances around 1.6 GeV. The structure in 13 −− is considered to be the π 3 (1690).
Result of single Breit Wigner fit around 1.6 GeV. Called here $M(1635).
Results of double Breit Wigner fit around 1.6 GeV. $M(1446) and $M(1701).
Result of Breit Wigner fit around 1.7 GeV.
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.
ACCEPTANCE CORRECTED.
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