The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

We present and discuss a set of systematic measurements, carried out with gaseous proportional micro-pattern detectors, in order to assess their maximum gain when irradiated with high-rate soft X-rays and heavily ionizing alpha particles. The inventory of detectors tested includes: microstrips, micromegas, micro-dot, gas electron multiplier, CAT (compteur à trous), trench (or groove), micro-CAT (or WELL) detectors, as well as systems with two elements of gaseous amplification in cascade. W e confirm the general trend of all single-stage detectors to follow Raether's criterion, i.e. a spontaneous transition from avalanche to streamer, followed by a discharge, when the avalanche size reaches a value of a few 10 7 ; a noticeable exception is the micro-dot counter holding more than 10 8 . In multiple structures, where the gain is shared between two devices i n cascade, the maximum overall gain under irradiation is increased by at least one order of magnitude; we speculate this to be a consequence of a voltage dependence of Raether's limit, larger for low operating potentials. Our conclusion is that only multiple devices can guarantee a sufficient margin of reliability for operation in harsh LHC running conditions.

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From measurements of the cross sections for eẽ-~hadrons and the cross sections and forward-backward charge-asymmetries for e e-~e + e-,~+-and s-r at several centreof-mass energies around the Z" pole with the DELPHI apparatus, using approximately 150000 2 = 0.0003±0.0010and A~= 0.2508±1)0027. These values correspond to the electroweak parameters: PCV = 1.003±0.011and sin20~j 0.241±0.009.Within the Minimal Standard Model (MSM). the results can he expressed in terms of a single parameter: sin20~=0.2338±0.0027.All these values are in good agreement with the predictions ot the MSM. Fits yield 43< m 115, < 215 0eV at the 95Vr level. Finally, the measured values of "z and arc used to derive lower mass bounds for possible new particles. * The VD, which was operated during most of the 1990 data collection period, was used in the alignment procedure of the barrel tracking detectors, but was not used directly in the analysis described here. * Fits with the formula of ref. [26] tend to underestimate M~and T~by about 2 MeV and to overestimate a'1~by approximately 0.1%.