118883948
FURTHER REMARKS ON THE $Sigma$ PARITY
Answers are given to some recent criticisms of the EPSILON parity determination made at the Lawrence Radiation Laboratory. (auth)
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.
123641336
Recoil detection with a polarized He-3 target
Abstract The ultra-thin gas targets used in storage ring internal target experiments allow low energy, heavy nuclei to emerge from the target region. A detector capable of analyzing these nuclei provides unique access to many nuclear reactions. We report here the first use of such a detector in conjunction with a polarized 3 He internal target and a polarized electron beam. The results of using the detector as a luminosity monitor and as a polarimeter to measure the product of beam and target polarizations are presented. The ability to study coherent pion production via the reactions 3 He → ( e → , e ′ 3 He )π 0 and 3 He → ( e → , e ′ 3 H )π + is shown along with the ability of the detector to unambiguously separate the two- and three-body breakup channels of the reaction 3 He → ( e → , e ′p) .
121914137
DECAY MODES AND WIDTH OF THE /eta/ MESON
Author(s): Bastien, Pierre L.; Berge, J. Peter; Dahl, Orin I.; Ferro-Luzzi, Massimiliano; Miller, Donald H.; Murray, Joseph J.; Rosenfeld, Arthur H.; Watson, Mason B.
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.
109046686
Beam incidents - High particle rate tests of an LHCb/Velo silicon strip module
L. Eklund ∗a, K. Akiba b, O. Behrendt c, M. van Beuzekom b, J. Buytaert c, P. Collins c, M. Ferro-Luzzi c, K. Hennessy d, J. Imong e aUniversity of Glasgow, Glasgow, UK. bNikhef, National Institute for Subatomic Physics, Amsterdam, Netherlands. cEuropean Organisation for Nuclear Research (CERN), Geneva, Switzerland. dUniversity of Liverpool, Liverpool, UK eH.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom. E-mail: Lars.Eklund@cern.ch
114023912
Performance of a wide pitch n-on-n silicon detector with floating strips
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.
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.
122010968
LUMINOSITY MONITORING AT LHCb