120004567
Performance of a hydrogen/deuterium polarized gas target in a storage ring
Abstract The performance of a high-density polarized hydrogen/deuterium gas target internal to a medium-energy electron storage ring is presented. Compared to our previous electron scattering experiments with tensor-polarized deuterium at NIKHEF (Zhou et al., Nucl. Instr. and Meth. A 378 (1996) 40; Ferro-Luzzi et al., Phys. Rev. Lett. 77 (1996) 2630; Van den Brand et al., Phys. Rev. Lett. 78 (1997) 1235; Bouwhuis et al., Phys. Rev. Lett. 82 (1999) 687; Zhou et al., Phys. Rev. Lett. 82 (1999) 687) the target figure of merit, ( polarization ) 2 × luminosity , was improved by more than an order of magnitude. The target density was increased by upgrading the flux of nuclear-polarized atoms injected into the storage cell and by using a longer (60 cm ) and colder (∼70 K ) storage cell. A maximal target thickness of 1.2 (1.1)±0.1×10 14 nuclei / cm 2 was achieved with deuterium (hydrogen). With typical beam currents of 110 mA , this corresponds to a luminosity of about 8.4 (7.8)±0.8×10 31 e − nuclei cm −2 s −1 . By reducing the molecular background and using a stronger target guide field, a higher polarization was achieved. The target was used in combination with a 720 MeV polarized electron beam stored in the AmPS ring (NIKHEF) to measure spin observables in electron–proton and electron–deuteron scattering. Scattered electrons were detected in a large acceptance magnetic spectrometer. Ejected hadrons were detected in a single time-of-flight scintillator array. The product of beam and target vector polarization, P e P t , was determined from the known spin-correlation parameters of e ′ p quasi-elastic (or elastic) scattering. With the deuterium (hydrogen) target, values up to P e P t =0.49±0.03 (0.32±0.03) were obtained with an electron beam polarization of P e =0.62±0.04 (0.56±0.03) as measured with a Compton backscattering polarimeter (Passchier et al., Nucl. Instr. and Meth. A 414 (1998) 4988). From this, we deduce a cell-averaged target polarization of P t =0.78±0.07 (0.58±0.07), including the dilution by unpolarized molecules.
120396510
Scintillation fiber hodoscope for topological triggering
A fast and precise scintillating fiber (SciFi) hodoscope based on KURARAY SciFi and HAMAMATSU multianode H6568 tubes was constructed to be used in DIRAC experiment (PS-212) at CERN for tracking and topological triggering information. The front-end electronics was custom developed to allow on-line discrimination after built-in dynamic cross-talk rejection. Preliminary tests of the detector using more than 300 read-out channels have shown an excellent stability and optimum performance for this system: a uniform detection efficiency of 98%, a 125 μm single hit and ∼0.5 mm two-hit space resolution, 0.6 ns time resolution.
122363991
Helicity structure in low- and intermediate-energy weak interaction
Abstract We report on the status of the measurements of the longitudinal polarization of positrons emitted by polarized 107 In and 12 N nuclei. Present results yield a lower limit of 306 GeV/c 2 (90 % CL) for the mass of a possible W gauge boson with predominantly right-handed couplings, if interpreted in the framework of the manifest left-right symmetric model. In addition, the helicity structure of the weak interaction is discussed on the basis of experimental results at low and intermediate energies in the leptonic, semileptonic and hadronic sectors. Whereas in the minimal manifest left-right symmetric extension of the Standard Model the results from collider experiments are superior to results from other experiments, experiments in the three sectors of the weak interaction yield complementary information on the helicity structure of the interaction if interpreted in general left-right symmetric models.
118445517
Search for Narrow Resonances in $\pi^- p$ Large Angle Elastic Scattering and in $\pi^- p$ Total Cross-section
121311258
Design and construction of high-frequency transition units for polarized deuterium internal targets
Abstract Radio-frequency transition units have been developed in order to produce vector and tensor polarized atomic deuterium beams. Transitions between various hyperfine states were generated using both a medium field transition unit and a resonant cavity structure as a strong field transition unit. Tests were carried out to determine the transition efficiencies of these units as function of radio frequency power, strength of the magnetic holding field, magnetic field gradient, and for the strong field unit, also as function of the position of the atomic beam in the cavity structure. A Stern—Gerlach source equipped with a medium and a strong field unit will provide a tensor polarized deuterium beam with the highest figure of merit at the minimum number of transition units. This polarization scheme allows for rapid reversal of tensor polarization while keeping the vector polarization fixed, and vice versa. The performance of the high-frequency transition units is described well by the results of a quantum-mechanical calculation. We will demonstrate that in a realistic internal target environment the efficiencies for the transitions between the 1–4, 2–6, and 3–5 hyperfine states exceeded in all cases 90% of the theoretical maximum polarization.
103525244
Quasielastic electron scattering from polarized He-3.
1648236
The LHCb VELO: status and upgrade developments
The VErtex LOcator (VELO) is the silicon microstrip vertexing and triggering sub-detector of the LHCb experiment. It consists of a series of forward disks with the active region extending to just 8 mm from the LHC beams. The current status of the VELO is presented. Due to the high radiation environment, the VELO may have to be replaced after some years, possibly with new materials. A candidate material is Czochralski silicon. We present here promising new results on the first test beam of a large, high resistivity Czochralski microstrip silicon detector read out with LHC speed electronics. The performance was studied before and after irradiation with high energy protons. A signal to noise of over 20:1 was obtained from the detector and significant charge collection efficiencies were measured at relatively modest voltages after a fluence of 4.3/spl times/10/sup 14/ 1 MeV neutron equivalents (n/sub eq/) per cm/sup 2/. Studies using the Transient Current Technique probed the electric field within MCz test detectors and proved that MCz silicon does not type invert up until a radiation level of at least 5/spl times/10/sup 14/ 24GeV/c p/cm/sup 2/. This would mean the VELO could possibly replace, in a potential upgrade, n/sup +/-on-n DOFZ sensors and the complicated processing involved, for standard p/sup +/-on-n processing with MCz.
15273175
The LHCb trigger strategy and performance
Precise measurements of CP-violating asymmetries, oscillation parameters and branching ratios on numerous B-decay channels will allow an overdetermination of CKM parameters, with possible inconsistencies pointing to physics beyond the Standard Model. In order to achieve this, an experiment capable of triggering on the various decay modes of B-mesons (in particular hadronic modes) is desirable. LHCb [ 1] is an experiment dedicated to such precision studies at the large hadron collider (LHC). It is designed as a forward spectrometer, because BB pairs are expected to be predominantly produced at small polar angles. An overview of the LHCb detector and trigger scheme is shown in Figure 1.
114023912
Performance of a wide pitch n-on-n silicon detector with floating strips
122010968
LUMINOSITY MONITORING AT LHCb
208345688
VELO Geometry Optimisation
New possible layouts of the LHCb Vertex Locator (VELO) have been compared with the existing baseline design outlined in the Technical Proposal. Based on a comparison of essential figures of merit, namely vertex resolutions, event selection efficiencies, trigger performance, and technical constraints an updated baseline design is proposed. The new design retains the same number of electronic channels as that in the Technical Proposal, but has an increased number of measuring stations (25 rather than 17) with a reduced inner radius (8mm rather than 10mm).