Production rates of multijet hadronic final states are studied ine+e− annihilation at 29 GeV center of mass energy. QCD shower model calculations with exact first order matrix element weighting at the first gluon vertex are capable of reproducing the observed multijet event rates over a large range of jet pair masses. The method used to reconstruct jets is well suited for directly comparing experimental jet rates with parton rates calculated in perturbative QCD. Evidence for the energy dependene of αs is obtained by comparing the observed production rates of 3-jet events with results of similar studies performed at higher center of mass energies.
Observed production rates relative to the total hadronic cross section.
Production rates corrected for fragmentation, initial state radiation and detector effects.
The reaction e + e − → τ + τ − has been studied at centre of mass energies between 14.0 and 46.8 GeV with the CELLO detector at the PETRA e + e − collider. We present results for the cross section σ τ and the charge asymmetry A τ . The results are in good agreement with the standard model. We have also measured the topological decay rates BR 1 , BR 3 and BR 5 for the inclusive decay of the τ lepton into one, three and five charge particles. The results confirm and improve earlier CELLO measurements at other energies. We find for the combined values at all energies BR 1 = (84.9 ± 0.4 ± 0.3)%, BR 3 = (15.0 ± 0.4 ± 0.3)% and BR 5 = (0.16 ± 0.13 ± 0.04)%.
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Corrected for radiative effects and background contributions.
Fermilab experiment 711 has investigated proton-nucleus collisions in which two high-transverse-momentum hadrons are produced forming high-mass ++, +-, and -- charged states, using an 800-GeV/c proton beam on targets of beryllium, aluminum, iron, and tungsten. Our data cover the range in dihadron mass from 6 to 15 GeV/c2. We show here that the dependence of the cross section on atomic weight A can be parametrized as Aα where α=1.043±0.011(stat)±0.025 (syst), and is independent of the charge state of the dihadron system.
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We present results on Λc+ production in 29-GeV e+e− annihilation. The Λc+ are observed via their semileptonic decays to Λe+X and Λμ+X. With radiative corrections, we find σ(e+e−→Λc+X)〉BΛc+→eΛX)= 1.5±0.6±0.5 pb or 0.0038±0.0015±0.0012 Λc+→Λe+X decay per hadronic event, and σ(e+e−Λc+X)B(Λc+→μΛX)= 1.4±1.4±0.4 pb or 0.0035±0.0035±0.0011 Λc+→Λμ+X decay per hadronic event. These results can be used to place constraints on the predictions of various production models.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA E+ decay channel.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA MU+ decay channel.
Using the ARGUS detector at thee+e− storage ring DORIS II, we have investigated inclusive production of π±,K±,Ks0 and\(\bar p\) in multihadron events at 9.98 GeV and in direct decays of the ϒ(1S) meson, i.e. from quark and gluon fragmentation. The most pronounced difference is the rate of baryon production. The Lund Monte Carlo program gives a reasonable qualitative description, although it cannot reproduce our data in detail.
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Calorimeter measurements of dσ de t for pp, dd, pα , and αα collisions at S nn =31.5 GeV are presented for the pseudorapidity interval | η cm | ⩽ 0.7, extending over eight decades to E t ⩾ 30 GeV. The data are compared with models that predict nuclear cross sections directly from pp data, under the assumption of independent nucleon scatters.
The distributions are fitted D(SIG)/D(ET)=CONST*ET**POWER*EXP(-SLOPE*ET).
The reaction pp→p f (K + K − K + K − )p s in which the K + K − K + K − system is centrally produced has been studied at 300 GeV/ c . φφ production has been observed and the ratio σ (φK + K − )/ σ ( φφ ) is 1.0±0.3. The cross section for central production of φφ is found to be the same at 300 GeV/ c and 85 GeV/ c . An angular analysis of the φφ system favours J P =2 + over 0 − .
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A new determination of the u valence quark distribution function in the proton is obtained from the analysis of identified charged pions, kaons, protons and antiprotons produced in muon-proton and muon-deuteron scattering. The comparison with results obtained in inclusive deep inelastic lepton-nucleon scattering provides a further test of the quark-parton model. The u quark fragmentation functions into positive and negative pions, kaons, protons and antiprotons are also measured.
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The spin-dependent observables N 0 s ″ kn , D 0 n 0 n and K 0 s ″ k 0 in pp elastic scattering were measured at nine energies between 0.84 and 2.1 GeV using the SATURNE II polarized proton beam and the Saclay frozen spin polarized target. The beam polarization was oriented longitudinally and the target polarization was oriented vertically. Precession of the recoil particle spin in the target holding field introduces a small contribution from other parameters. The present results for K 0 s ″ k 0 and D 0 n 0 n agree with our previous measurements of the same observables carried out in different beam and target spin configurations as well as with previously existing measurements. The observable N 0 s ″ kn had not been measured previously above 0.58 GeV. Below 1.3 GeV our data are compared with the predictions of the Saclay-Geneva phase shift analysis. The new results will considerably affect the phase shift analysis solutions and will contribute to their extension towards higher energies.
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The spin-dependent observables D 0 n 0 n and K 0 nn 0 in pp elastic scattering were measured at 11 energies between 0.84 and 2.7 GeV using the SATURNE II polarized proton beam and the Saclay frozen-spin polarized target. The beam and target polarizations were oriented along the normal to the scattering plane. Below 1 GeV the present data agree with previously existing measurements. Below 1.3 GeV they are compared with the predictions of the Saclay-Geneva phase-shift analysis. The results will improve the phase-shift analysis solutions and will contribute to their extension towards higher energies.
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