No abstract available

No abstract available

[en] We have observed charmed D meson production from a hydrogen target in a 217 GeV/c π^- beam. Hadronic decays in the K^+-π^+-π^+- channels were reconstructed in the Chicago Cyclotron Spectrometer at Fermilab. The proton recoil angle and momentum transfer were programmed so that objects of mass near that of two D mesons would be produced in the forward direction. A mass peak in the 40-MeV bin at 1875 MeV was found in each channel. The cross section for D^+- production is 6--10 μb

[en] Branching ratios for the decay tau -> ν + (n pions) with n >= 2 are presented. The new data include all possible charge configurations of the pion system and, in particular, final states containing one or several neutral pions. The data are compared with predictions from CVC (even number of pions in final state) and current algebra (odd number of pions). They strongly support the standard coupling of the tau to the weak charged current. (orig.)

[en] The production of prompt leptons at PETRA has been measured for c.m. energies of 14, 22 and 34 GeV. The rate of prompt electrons and muons is presented, including a determination of the semileptonic branching ratio of the c and b quarks. We obtain B(c->μνX)=12.3+-2.9(stat.)+-3.9(syst.)%, B(b->μνX)=8.8+-3.4(stat.)+-3.5(syst.)%, B(b->eνX)=14.1+-5.8(stat.)+-3.0(syst.)%. Systematic effects due to changes in fragmentation and other model parameters have been studied. (orig.)

[en] We have measured the scale invariant inclusive photon and π⁰ cross sections at W = 14, 22 and 34 GeV. A comparison with π^+- data shows no significant difference between neutral and charged pion production. Comparing the integrated cross sections in the x range 0.15 < x < 1.0 we observe a considerable decrease from 14 GeV to 34 GeV with a statistical significance of 1.5 standard deviations. This is compatible with the expectations for scaling violations from QCD. (orig.)

[en] The production of prompt leptons at PETRA has been measured for c.m. energies of 14, 22 and 34 GeV. The rate of prompt electrons and muons is presented, including a determination of the semileptonic branching ratio of the c and b quarks. Systematic effects due to changes in fragmentation and other model parameters have been studied. (orig./HSI)

[en] At PETRA we have measured the process e + ß -> e + epsilon⁺ + epsilon^-, where epsilon is either an electron or a muon, at an average Q₂ of 9.5 GeV₂/c₂. The total number of events is 240. We find that our data agree with QED predictions based either on exact Feynman graph calculations or on the photon structure function expressions. (orig.)

[en] We have determined the cross section for γγ -> π⁺π⁺π^-π^- in a way free of assumptions about the relative contributions from rho⁰rho⁰, rho⁰2π and 4π (uncorrelated phase space). We find a sharp onset above threshold and a rather high cross section of about 200 nb around Wsub(γγ) = 1.5 GeV which consists to about 40% of rho⁰rho⁰ production with sizeable contributions from rho⁰2π and 4π (P.S.). The total cross section as well as the rho⁰rho⁰ content fall rather fast at higher c.m. energies. Attempts to explain this behaviour in terms of production of known resonances are not successful so far. The angular distributions do not show any significant structure pointing to resonance formation in the 4π-system. Only the rho⁰-meson is observed in the moment analysis. The decay distributions of the rho⁰ for forward produced rhos are fairly consistent with helicity conservation of the produced rhos in accordance with the VDM picture. (orig.)

[en] Two photon final states in e⁺e^- annihilation have been analyzed at CM energies around 34 GeV. Good agreement with QED is observed. Lower limits for the QED cutoff parameters of ßsub(+) > 59 GeV and ßsub(-)> 44 GeV are determined. A search for two photons with missing energy yields an upper limit for the production of neutral particles which decay into a photon and a non-interacting particle. Constraints on the mass and the coupling strength of supersymmetric photinos are discussed. (orig.)