Cross sections are presented for the inclusive production of Λ hyperons in electron-positron annihilations at s=29 GeV based on the full 291-pb−1 sample of data taken in the High Resolution Spectrometer experiment at the SLAC e+e− storage ring PEP. These results, and the associated correlation analyses, are consistent with the Lund model predictions with the strange diquark suppression ratio δ fixed at 0.59±0.10±0.18, as compared to the standard Lund value of 0.32. The Λ multiplicity has been found to be 0.182±0.020 per event. The opposite-strangeness multiplicity 〈nΛΛ¯〉 has been measured to be 0.046±0.020, whereas the like-strangeness multiplicity 〈nΛΛ+Λ¯Λ¯〉 is 0.009±0.028. A strong correlation is found between Λ's and Λ¯'s; when one is found in an event, the other is found in the same event with a probability that exceeds 50%.
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Extrapolate to full z interval using Lund fit.
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The elementary ¯p-neutron amplitude has been obtained from Glauber's model analysis of ¯p-d elastic scattering data at 600 MeV/c, taking into account theD-state component of the deuteron. The results are compared with the ¯p-nucleus analysis and the ¯NN potential model predictions.
No description provided.
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Antiproton induced fission probabilities of U238, Bi209, Pb208 and Au177 are reported together with the mass distribution of the fission fragments in the U238 and Bi209 cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.
TOTAL AVERAGE MASSES AND KINETIC ENERGIES OF FISSION FRAGMENTS. Mean mass is in proton mass units.
Distributions of event shape variables obtained from 120600 hadronicZ decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, αs(MZ), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model.
Experimental differential Thrust distributions.
Experimental differential Oblateness distributions.
Experimental differential C-parameter distributions.
Measurements are reported of inclusive production of η-mesons in the beam fragmentation region in γp, πp andKp collisions. Results include a small but significant departure from VMD, and a pronounced rise in theη/π0 ratio with increasingpT.
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Differential cross sections for the neutral pion production reaction C12(p,π0)13Ng.s. have been measured at 153.5, 166.1, 186.0, and 204.0 MeV bombarding energy using recoil detection. The shape of the angular distribution agrees well with that of the mirror reaction C12(p,π+)13Cg.s.. Isospin invariance predicts for the ratio of the cross sections σ(p,π+)/σ(p,π0)=2. At 153.5, 166.1, and 186.0, MeV, where (p,π+) cross sections have been reported previously by other groups at the same reduced pion momentum η=pπ/mπc=0.34,0.55,0.78, the ratio of the total cross sections is 2.02±0.14, 3.14±0.12, and 2.12±0.16, respectively. The (p,π0) cross sections at 166 MeV is therefore 1.57±0.06 times larger than expected. For Tp<160 MeV, the experimental cross sections are larger than predicted by a phase space and Coulomb barrier penetration calculation that fits the higher-energy data. Differential cross sections were also obtained for the C12(p,π−)13O reaction, and upper limits set for differential cross sections for radiative capture to the ground state of N13.
No description provided.
Inclusive inelastic scattering spectra from C, Ca, Sn, and Pb were measured for 100-MeV pions at a number of angles. The observed ratios of the π− and π+ total inelastic cross sections for the different targets are explained in terms of a simple model which is based on the assumption that the scattered pion has interacted with only one nucleon. This model also accounts for the ratio between normal and charge-exchange scattering cross sections at 100 MeV.
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The production of neutral pions has been studied in the 16 O+ 27 Al, 58 Ni, 208 Pb reactions at 95 MeV/nucleon. Inclusive pion differential distributions d σ d p t , d σ d T π , and d σ d Ω have been measured by detecting the two-pion decay γ-rays in a setup of 8 lead glass Cherenkov detector telescopes. The data are discussed in the framework of a moving thermal source model. It is shown that the shape of the pion energy spectra is better described if mean field effects on the primary pion-production cross section and pion reabsorption are included in the calculation.
Axis error includes +- 10/10 contribution.
SPECTRA WERE FITTED USING THE FORMULA D3(N)/D3(P)= CONST/(EXP(EKIN(P=3)/T)-1).
Axis error includes +- 10/10 contribution.
Enhanced strange particle production, nonstatistical multiplicity fluctuations and two-pion Bose-Einstein correlations were measured in O, S-nucleus reactions at 60 and 200 GeV/nucleon. The results indicate significant collective effects in high-energy nucleus-nucleus collisions.
CENTRAL COLLISIONS.
CENTRAL COLLISIONS.
Product of charged kaons in central S + S and O + Au collisions at 200 GeV/nucleon has been studied in the NA 35 Streamer Chamber experiment. Mean multiplicities and transverse mass distributions were obtained. They were compared with nucleon-nucleon data and with model predictions.
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