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).
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.
120619277
Spin-dependent electromagnetic response of few-body systems.
We report on the experimental program with polarized electrons and polarized few-body systems at the internal target facility of the NIKHEF electron storage ring. 
 
With a polarized deuterium internal target, absolute measurements of unprecedented accuracy have been performed for the analyzing powers T20 and T22 in elastic electron-deuteron scattering at transferred four-momenta 1.1 < Q < 2.8 fm−1. Results for a first measurement of the tensor analyzing power in quasi-elastic scattering are also presented. These data provide new constraints for descriptions of the deuteron spin structure and for reaction mechanism effects. 
 
Quasi-elastic electron scattering from polarized 3He may provide precise information on the S′ and the D-wave parts of the 3He ground-state wave function, the neutron form factors, and the role of spin-dependent reaction mechanism effects. We have started an experimental program at NIKHEF where polarized 3He and polarized electrons are used, in combination with large acceptance electron and hadron detectors. Data were taken for the transverse (Ay0) and longitudinal (A′z) asymmetries at Q ⋍ 2 fm−1. We outline the performance of the target and detectors.
117922305
Measurement of spin correlation parameters in the Delta region for the H-1(pol.)(e(pol.),e') reaction
Sensitivity to the quadrupole transition form factors (C2 and E2) of the N-Delta excitation can be obtained by measuring double-polarization electromagnetic observables in the Delta-region. Such measurements have been carried out with the internal target facility at NIKHEF. Radiative corrections are an important ingredient of the data interpretation. They need to be evaluated carefully, taking into account their spin-dependence, in order to compare the data to theoretical models of pion electroproduction. From these comparisons the E2/M1 and C2/M1 ratios can be extracted.
121481841
Excited Hyperon of Mass 1520 Mev
Investigations of the K-p interaction at about 400 Mev/c were made. Cross seetions for K- momenta were measured, and momentum dependence of the cross section for reactions K- + p - A + pi /sup +/ + pi - and K- + p - K + n was observed. Existence of an excited hyperon with l520 plus or minus 3 Mev mass, r/2 = 8 Mev half width, 0 isotopic spin, even parity with respect to K-p (D,.), and branching ratios of KN: SIGMA pi of DELTA 2 pi = 3 of 5: 1 was established. (L.N.N.)
122181300
Proposal for an absolute luminosity determination in colliding beam experiments using vertex detection of beam-gas interactions
Abstract We propose a method for determining the absolute luminosity in a colliding-beam experiment at circular accelerators by measuring vertices of beam–gas interaction to determine the beam shapes and overlap. This method can be applied (for example) at all Large Hadron Collider experiments without modification of their detectors.
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.