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.
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In order to modify the present SOOMeV, 1% duty factor electron accelerator MEA into a 900MeV, 0.1 % d.f. injector for a newly to be build pulse-stretching ring, the present modulator-klystron units have to be adapted from 4MW, 2% d.f. mode of operation into the 10MW, 0.2% d.f. mode.Suitable klystrons are commercially availabe, the matching modulators, however, will be obtained by modifying the present ones, which policy is dictated by economical considerations.The design principles of these modulators -a proto-type is presently under construction-will be discussed. Special attention is given to the video-pulse shape requirements, dictated by the future performance of the pulse-stretcher. This device has to deliver low emittance, high duty factor (-90%) beams for nuclear physics experiments, Some proto-type tests of the video-pulse forming modifications will be presented.
We report on first measurements with polarized electrons stored in a medium-energy ring and with a polarized internal target. Polarized electrons were injected at 442 MeV (653 MeV), and a partial (full) Siberian snake was employed to preserve the polarization. Longitudinal polarization at the interaction point and polarization lifetime of the stored electrons were determined with laser backscattering. Spin observables were measured for electrodisintegration of polarized 3 He, with simultaneous detection of scattered electrons, protons, neutrons, deuterons, and 3 He nuclei, over a large phase space.PACS numbers: 24.70. + s, 25.30.Fj, 29.20.Dh, 29.27.Hj In the scattering of leptons from hadronic targets, the leptonic part of the interaction is well understood, allowing one to focus on the strong-interaction vertex and the underlying structure and dynamics of the nucleus. The ultimate probe consists of spin-dependent scattering with polarized leptons and polarized targets [1], and the last decade has seen a large effort devoted to the realization of such experiments.Most experiments used electrons beams impinging on external polarized targets to achieve adequate luminosity. In this way, data on, e.g., the neutron form factors and deep-inelastic structure functions have been obtained (see, e.g., [2][3][4][5][6][7]). Although typically lower in luminosity, spindependent electron scattering experiments from polarized gas targets internal to storage rings have the advantages: (i) they can be well matched with the use of large-acceptance detectors; (ii) rapid polarization reversal and flexible orientation of the nuclear target spin can be obtained, reducing systematical uncertainties; (iii) low-energy recoiling particles can escape the ultrathin targets and can be detected, allowing a complete reconstruction of the final state in the electrodisintegration of few-body systems. So far, electromagnetic spin-correlation observables from internal gas target experiments have been obtained only at DESY [7] in the deep-inelastic scattering regime. There the electron beam energy is high enough that transverse polarization builds up through the Sokolov-Ternov effect [8].For a study of nuclear structure and dynamics in both the quasifree scattering and D-resonance region, electron beams with energies up to 1 GeV are optimal: one may achieve resolutions in energy and momentum sufficient to distinguish various nuclear states and details in the wave functions; one can keep the momentum transfer small to optimize the sensitivity to long-distance nucleon and nuclear physics effects, while detection of heavily ionizing recoiling nuclear particles yields increased sensitivity to coherent effects in the nuclear dynamics. However, for such low electron beam energies the self-polarizing time is too long to take advantage of, and one has to inject polarized electrons and rely on Siberian-snake techniques. An experiment with the VEPP-2M collider at BINP, Novosibirsk [9], demonstrated that with such a solenoid (i.e., snake) the polarization...
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