No abstract available

[en] An 80 GeV electron beam has been used to generate plane polarised photons by means of coherent bremsstrahlung in a silicon crystal. The photons are tagged in the energy range 25-70 GeV, and have been used in a photoproduction experiment at the Omega Spectrometer at CERN. (orig.)

[en] A total of 110 drift chambers, each containing two 60 cm wide drift cells with anode wires up to 10.4 m long, have been installed on the OPAL detector at the LEP electron-positron collider in CERN, Geneva. The chambers allow measurement of space points on the trajectory of a charged particle: Coordinates transverse to the wire direction are reconstructed to an accuracy of 2 mm using conventional drift-time measurements, while a novel arrangement of diamond shaped cathode pads allows location of the track along the wire to an accuracy of 1.5 mm. This is achieved by three measurements of increasing ambiguity but also increasing accuracy. The techniques developed to analyse the signals from the cathode pads are described in some detail. (orig.)

[en] Experimental results are presented on the pair production from high-energy photons (40-150 GeV) incident on a 0.5 mm Ge single crystal around the <100> axis. The observed enhancement increases from around 1 at threshold (40 GeV) to 7 at 150 GeV for photons aligned with the axis. Also the angular dependence and the differential e⁺/e^- spectra have been studied. For photons aligned with the axis, the results are in good agreement with calculations based on the constant field approximation. (orig.)

[en] The first results from a broad angular beam experiment on emission of high-energy photons from 170 GeV electrons and positrons are presented. The targets were 0.5 mm thick Si and Ge crystals. A dramatic enhancement in the emitted radiation is found for angles of incidence close to the <110> axis. The experimental results are compared to a constant-field cascade calculation. (orig.)

[en] A study is made of the ωπ⁰ system produced near threshold in the reaction γp -> π⁺π^-π⁰π⁰p. A spin-parity analysis shows that the ωπ⁰ enhancement is consistent with predominant 1⁺ B(1235) production, with proportional 20% Jsup(P) = 1^- background. (orig.)

[en] Further experimental evidence is given for the F meson through its decay into eta's. Results are presented for the decay channels etaπsup(+-), etaπ⁰πsup(+-) and etaπ⁺π^-πsup(+-), and confirm those obtained in a previous experiment. (orig.)

[en] The reactions γp -> K⁺K^-π⁰(p) and γp -> Ksub(S)⁰Ksup(+-)πsup(-+)(p) have been measured using tagged photons in the energy range 20 to 70 GeV. No resonance structure is observed in either of the Kanti Kπ invariant mass distributions, which range from threshold up to approx.= 3 GeV. The photoproduction cross section for PHIπ⁰ and Ksup(*)(892)K are presented and are compared with theoretical predictions. No evidence has been found for the photoproduction of PHI'(1680). (orig.)

[en] Inclusive production of rho⁰, ω, and rhosup(+-) at low transverse momentum has been measured in γp collisions with photons of energy 20 to 70 GeV. The vector mesons have been studied as functions of the Feynman variable chisub(F), varying between -0.2 and 0.95, i.e. excluding the 'elastic' peaks of rho⁰ and ω photoproduction. For chisub(F) < or approx. 0.6 the vector meson cross sections are approximately equal; that is, sigma (rho⁰) approx.= sigma (ω) approx.= 1/2[sigma(p⁺) + sigma(p^-)]. For chisub(F) > 0.6, it is observed that sigma(p⁰) > sigma(ω) >=1/2[sigma(rho⁺)+sigma(rho^-)] and the differences increase with increasing chisub(F). Over the rhosub(F) range -0.2 < mesons are produced similarly to non-diffractive leading particles in hadron-hadron collisions with an extra diffractive component in rho⁰ and ω production. (orig.)

[en] A rhoπ enhancement with mass 1.67 +- 0.02 GeV and width 0.16 +- 0.02 GeV is observed in the channel ßp -> pπ⁺π^-₀. Assuming an incoherent background, the cross section x branching ratio is 100 +- 20 nb. A spin-parity analysis favours Jsup(P) = 1^-. The enhancement is most simply interpreted as a radial recurrence of the ß meson. (orig.)