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.
No description provided.
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We have measured the spin-transfer parameters KLL, KSL, KLS, and KSS at 635 MeV from 50° to 178° c.m. and at 485 MeV from 74° to 176° c.m. These new data have a significant impact on the phase-shift analyses. There are now sufficient data near these energies to overdetermine the elastic nucleon-nucleon amplitudes.
Spin transfer parameters from np elastic scattering at 635 MeV. There is an additional overall normalisation of 2 PCT.
Spin transfer parameters from np elastic scattering at 485 MeV. There is an additional overall normalisation of 2 PCT.
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.
No description provided.
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We have measured the cross section for γγ production with the TOPAZ detector in the energy region √ s =50.0–61.4 GeV. The observed cross section for γγ production integrated over |cos θ | ⩽ 0.77 is 50.2±0.8±2.2 pb at 〈√ s 〉=57.6 GeV and the ratio of this value to the QED prediction is 1.01±0.02±0.04. The angular distribution is in good agreement with the QED predictions, thereby setting limits on the compositeness scales, Λ L+R + =168 GeV, Λ L+R − =97 GeV, Λ L,R =141 GeV, Λ L,R − =81 GeV, and Λ L−R ± =68 GeV, at the 95% confidence level. The reaction e + e − → γγγ was also studied and was found consistent with the QED prediction.
No description provided.
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We have measured the K + K - /π + π - ratio R from p annihilations in gaseous D 2 and H 2 at atmospheric pressure. The measurement was performed with the OBELIX spectrometer. From the measured value in gaseous D 2 (0.27±0.02) we infer a P wave contribution to p −p annihilation in D 2 of (18±7)%.
Two different triggers were used.
Data collected in the experiment R704 at the CERN ISR are used to study the annihilation process p p → π 0 π 0 at several centre-of-mass energies between 2.97 and 3.56 GeV. A total sample of 7359 events has been identified, from which cross sections and angular distributions in the interval 0 < | cos θ ∗ | < 0.5 have been measured.
No description provided.
No description provided.
Backward emitted protons with momentump>0.3 GeV/c in interactions of neutrino in the energy range 10–200 GeV with photoemulsion nuclei were investigated. Energy spectrum slope parameter of backward protons was measured to beT0=48.9±7.9 MeV. TheA-dependence power index of relative mean yield of backward protons was found to bea=0.68±0.12. A drop in the mean yield of backward protons at the four momentum squared over ∼15 (GeV/c)2 (the neutrino energy over ∼50 GeV) was observed.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
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