No abstract available

No abstract available

No abstract available

[en] Results are presented for the quasi two-body hypercharge exchange reactions of the type 0^-1/2⁺→1^-3/2⁺(K^-p→rho^-Σ⁺(1385) K^-p→phiΣ⁰(1385)) and 0^-1/2⁺→1^-3/2^-(K^-p→ωΛ(1520) K^-p→phiΛ(1520)) using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions. (Auth.)

[en] In this letter results are presented on the reactions K^-p→anti K⁰n and K^-p→K^-p from a high statistics CERN 2 m etre hydrogen bubble chamber exposure a t 4.15 GeV/c. The behaviour of the differential cross section as a function of four-momentum transfer shows remarkable similarities between the two reactions studied. From a comparison of the data with K⁺p elastic scattering at 4.27 GeV/c some conclusions are drawn concerning the magnitude of the contributing amplitudes. (Auth.)

[en] The gating system of the MWPCs of the DELPHI Barrel RICH is essentially a means to prevent positive ions originating from avalanches in the chambers to escape into the Barrel RICH drift tubes. These ions would otherwise seriously affect the imaging quality of the Barrel RICH. We describe the gating grid, the gating pulser and results of tests at pressures of 1 and 1.3 bar in a magnetic field of 1.2 T and without. In the ungated ('closed') mode, transfer of electrons and ions are 8% and 0% respectively; a further reduction of electron transfer is limited by power dissipation of the pulsing circuit. The occupation time of the readout electronics after the gating pulse is less than 1 μs. The test results are compared with those of electrostatic simulations. A triggering scheme is proposed. (orig.)

[en] We discuss the performance of multiwire proportional chambers to be used as photoelectron detectors on the Barrel Ring Imaging Cherenkov counter of the LEP DELPHI spectrometer. The chamber is used for the 3-dimensional localization of Cherenkov photons and can be gated by means of a pulsed grid. It has been operated in a 10 GeV/c π^- test beam setup allowing the production and the detection of Cherenkov light. With an isobutane gas radiator, we have measured a 93% relative cathode efficiency, a quality factor N₀=89 cm^-1 and a Cherenkov angle resolution of 3.9 mrad, in good agreement with Monte Carlo simulation. (orig.)

[en] We describe a method to monitor ageing effects in the multiwire proportional chambers (MWPCs) of the barrel ring imaging Cherenkov (BRICH) detector of DELPHI. It is based on a measurement of plateau-curve characteristics and the shift of these as a function of the total collected charge. Results indicate that, as yet, no ageing effects are present. (orig.)

[en] We describe a simple method to survey effects of ageing in the multiwire proportional chambers of the DELPHI Barrel Ring Imaging CHerenkov (RICH) counters. These chambers detect single photoelectrons created by Cherenkov light in a photosensitive gas mixture. They receive as well the much larger amount of ionisation electrons created by the charged particles. The method essentially consists of a comparison of the plateau curves measured after each year's running period in order to detect changes in their characteristics as a function of exposure. ((orig.))

[en] The European Hybrid Spectrometer is described in its preliminary version for the NA16 charm experiment. The performance of the small hydrogen bubble chamber LEBC and the detectors of the spectrometer is discussed. In particular the combination of the bubble chamber information with the spectrometer data is described in detail. The track reconstruction efficiency is 90%. The precision with which vertices seen in the bubble chamber are reconstructed is around 10 μm and the two track resolution is 40 μm. Therefore very complex event configurations, in particular charm particle decays, can be reconstructed correctly. (orig.)