No abstract available

[en] The backward elastic scattering reaction π^-p→pπ^- at momenta 25 and 38 GeV/c have been measured using a magnetic spectrometer with hybrid chambers. The experimental data on the dependence of the cross section dsigma/du on the momentum transfer u as well as the energy dependence dsigma/du at u=O are given. (Auth.)

No abstract available

[en] As part of the NA24 experiment at the CERN-SPS a photon position detector serves to separate direct photons from abundantly produced π⁰ decay photons: electromagnetic showers are measured with an energy- and position-resolution sufficiently good to give a two-gamma resolving power of 1.2 cm. The shower detector covers 3 x 3 m² and consists of 12 layers of triangular proportional tubes (7.73 mm pitch) sandwiched with lead (altogether 9.6 X₀). For eight layers the analog information is provided by an ADC system. Ambiguities are resolved by the digital information of four additional layers inclined by 45⁰. Prototypes were built in order to test gas mixtures and electronics. The electromagnetic shower development in the PPD and the prototypes are reproduced by Monte Carlo calculations. The homogeneity of the PPD has been checked by calibration measurements. (orig.)

[en] The results of a simulation of the response of the L3 detector to hadrons is presented. The simulation is made on the basis of data obtained in the beam with the setup consisting of a uranium gas-sampling calorimeter with a bismuth germanium oxide calorimeter in front of it. (orig.)

No abstract available

[en] The performance of a uranium gas sampling hadron calorimeter is described. It has been observed that the hydrogen content of the gas mixture plays an important role in defining the behaviour of this type of calorimeter. The low-energy neutrons emerging from a hadron cascade are detected much more efficiently in a hydrogenous gas; thus leakage or containment of these neutrons becomes an important feature of the calorimeter setup. (orig.)

[en] A prototype of a gas sampling uranium module of the L3 hadron calorimeter was built and subsequently tested with pion beams of energies between 4 and 20 GeV. The construction of the proportional chambers, the assembling of the module, the readout electronics, and the beam test are briefly described. The energy resolution of the calorimeter module alone was measured to be 30.5±3% at 6 GeV, 21±2% at 10 GeV and 18±2% at 20 GeV. For the module together with a BGO crystal matrix in front, the resolution was 29±3% at 4 GeV, 21±2% at 10 GeV, and 17±2% at 20 GeV. (orig.)

[en] Cross sections for inclusive π⁰-production at large transverse momentum, p_T, were measured in π^-p, π⁺p and pp collisions at 300 GeV/c. The cross section ratio σ(π^-p→π⁰X)/σ(π⁺p→π⁰X) was found to be consistent with unity in the p_T region of 1 to 5 GeV/c. The cross section ratio σ(π⁺p→π⁰X)/σ(pp→π⁰X) however is growing with increasing pT and increasing π⁰ c.m.s. rapidity in agreement with parton model expectations, where the partons in the pions have on average higher momenta than in the proton. (orig.)

[en] Cross sections for inclusive direct photon production in π^-p, π⁺p and pp collisions at 300 GeV/c are measured at transverse momenta, p_T, up to 7 GeV/c (x_T = 0.6). For π^-p → γx also the rapidity distribution is presented. The cross section ratio σ(π^-p → γx)/σ(π⁺p → γx) is found to be one at p_T = 4 GeV/c and rises with increasing p_T. This observation signals the occurrence of valence quark antiquark annihilation. The results are in good agreement with QCD predictions. (orig.)