We report final results on prompt electron production in hadronic events from e+e− annihilations at √s =29 GeV, obtained with the DELCO detector at the SLAC storage ring PEP. We find the semielectronic branching ratios of charm and bottom quarks to be B(c→se+νe)=(11.6−0.9 +1.1)% and B(b→ce−ν¯e)=(14.9−1.9 +2.2)% respectively. These results, from the complete data set, are consistent with an earlier analysis of partial data and indicate hard fragmentation functions for both c and b quarks, with mean values 〈zc〉=0.59±0.04 and 〈zb〉=0.72±0.05. The errors indicated here are a combination of statistical and systematic uncertainties.
Axis error includes +- 0.0/0.0 contribution (NOT GIVEN).
Axis error includes +- 0.0/0.0 contribution (NOT GIVEN).
Axis error includes +- 0.0/0.0 contribution (NOT GIVEN).
The polarization of Ξ− hyperons produced by 400-GeV protons in the reaction p+Be→Ξ−+X has been measured as a function of momentum at two production angles. The average polarization for the full sample (192 110 events) was -0.108±0.007. Comparisons are made with polarization measurements for other hyperons produced under similar conditions. From the same data, αΛαΞ was measured to be -0.303±0.004±0.004, where αΛ is the asymmetry parameter in the decay Λ→pπ−, αΞ is the asymmetry parameter in the decay Ξ−→Λπ−, and the uncertainties are statistical and systematic, respectively. This yields αΞ=-0.472±0.006±0.011, where the systematic uncertainty is dominated by the uncertainty in αΛ. An updated test of the ΔI=1/2 rule in Ξ decay is presented.
No description provided.
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Results are presented of a measurement of the production of D*+ (D*−) in 250-GeV/c π−N interactions. We observe 2.1±7.8 events corresponding to a charge-D* cross section σ(D*) of 0.4±1.5 μb/nucleon. When averaged with our previous measurement made at 200 GeV/c, the result is σ(D*)=2.3±1.0 μb/nucleon with (dσ/dx)‖x=0=4.6±2.0 μb.
THIS DATA FROM PREVIOUS PUBLICATION : PRL 46, 761 (1981).
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We use the reaction e+e−→hadrons, in the Mark J detector at the DESY electron-positron collider PETRA, to determine the hadronic cross section up to 46.78 GeV. The production of a top quark with a charge equal to (2/3) is excluded up to 46.6 GeV with 95% C.L. The observed rise in the cross section at higher energies is consistent with the electroweak prediction for a Z0 mass of 93 GeV. We describe some unusual muon inclusive events.
Errors are statistical only.
Energy scan of R.
Inclusive muon cross section.
New data are presented on charged particle multiplicity distributions for non single-diffractive events produced at CM energies s = 200 and 900 GeV . The data were obtained at the CERN antiproton-proton collider operated in a new pulsed mode. The multiplicity distributions are very well described by a negative binomial distribution. The highest energy data show no sign of approaching scaling, confirming our earlier results on the breaking of KNO scaling. The energy variation of the average charged multiplicity can be fitted to a quadratic in ln s or a s 0.13 dependence.
Figure gives uncorrected multiplicity distributions. Here we give the corrected distributions. Data supplied by D. Ward.
Results for multiplicity moments based on negative binomial fit to corrected data. Errors reflect both statistical and systematic effects. Results from earlier data at 546 Gev cm energy are also given.
C moments for corrected data where CQ=<N**Q>/<N>**Q.
A new technique is applied to data collected at the ψ(3770) resonance to derive charmed-D-meson branching fractions without relying on the measurement of D-production cross sections. Measurements are presented for three decay modes of the D0 (K−π+, D−π−π+π+, and K−π+π0 and four decay modes of the D+ (K−π+π+,K−π+π+π0,KS0π+, and KS0π+π0). The resulting branching fractions are significantly larger than previous measurements.
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We have observed decays of the ϒ(1S) into hadronic final states containing high-energy photons. These are interpreted as coming from the decay ϒ(1S)→γ+gluon+gluon. We compare the shape of the observed photon energy spectrum with several theoretical predictions and deduce the value of the strong-coupling constant αs and the QCD scale parameter ΛMS― (MS― denotes the modified minimal-subtraction scheme) associated with each prediction.
DATA TAKEN ON THE PEAK OF THE UPSI(9460).
DATA TAKEN ON THE PEAK OF THE UPSI(9460).
Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦PT≦6 GeV/c and center-of-mass rapidity −0.4≦y*≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given.
Data from conversion trigger. Statistical errors only.
Data from calorimeter trigger. Statistical errors only.
This paper presents a study of events produced in 29-GeV electron-positron annihilation in which there are just two noncollinear charged particles, no detected photons, and two or more undetected particles. These events can be explained by attributing them primarily to the reactions e+e−→e+e−e+e− and e+e−→e+e−μ+μ− where just two particles appear in the Mark II detector. There is no evidence for unconventional sources for such events.
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The absolute differential cross sections of 17.9 GeV/$c$ $\alpha$-particles scattering on nuclear targets have been measured over a four momentum transfer range of $0.009
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