119049564
Focusing of a 1-GeV proton beam as it is brought into the channeling regime by a curved single crystal
The possibility of focusing high-energy particles by means of bulk capture of particles in the channeling regime is demonstrated experimentally. Protons with energies of 1 GeV, as they were bulk captured by the (111) plane of a curved silicon crystal from an angular interval with FWHM = 7.2 mrad at the exit from the crystal, had an angular divergence with FWHM = 1.6 mrad. The phase space of the beam of channeling particles in this case decreased slightly (by a factor of 1.8).
118636693
Polarization effects in the quasielastic (p, 2p) reaction with the nuclear S-Shell Protons at 1 GeV
The polarization of the secondary protons in the (p, 2p) reaction with the S-shell protons of nuclei 4He, 6Li, 12C, 28Si, 40Ca was measured at 1 GeV unpolarized proton beam. The spin correlation parameters Cij for the 4He and 12C targets also were for the first time obtained as well. The polarization measurements were performed by means of a two-arm magnetic spectrometer, each arm of which was equipped with the multiwire-proportional chamber polarimeter. This experiment was aimed to study a modification of the proton-proton scattering matrix in the nuclear medium.
55963955
Study of aging properties of a wire chamber operating with high-pressure hydrogen
The project for a precision measurement of the mp-capture rate (mCAP experiment) is based on an application of a multi-wire proportional chamber (MWPC) operating in ultra-pure hydrogen at 10 bar pressure. A special test setup was constructed at PNPI to investigate the MWPC performance under the expected experimental conditions. The aging studies of the MWPCs were performed with intense irradiation from an a-source ð 241 AmÞ and a b-source ð 90 SrÞ: After 45 days of continuous irradiation by a-particles no changes in the currents, in the signal shapes, and in the counting rates were observed. It was demonstrated that the MWPCs can operate without degradation at least up to accumulated charges of 0: 1C =cm wire. These irradiation conditions are much more severe than in the real experiment. During the study of the MWPC we have observed an appearance of short duration signals with amplitudes an order of magnitude larger than those of normal signals from the a-particles. The number of such signals (‘‘streamers’’) strongly depend on HV. We shall continue these tests in the future with the goal of obtaining more detailed information about aging properties of MWPCs operating with high-pressure hydrogen.
125792222
THE ELECTRON TRANSITION RADIATION DETECTOR IN THE EXPERIMENT TO MEASURE THE ASYMMETRY IN THE BETA DECAY OF POLARIZED SIGMA- HYPERONS
102408955
THE INVESTIGATION OF THE DRIFT CHAMBER EFFICIENCY OPERATING IN PURE HYDROGEN AND HELIUM FOR PRESSURES UP TO 9-ATM
121193004
Study of nuclear medium effects on polarization in (p, 2p) scattering at 1 GeV
We report on experimental investigation of the (p, 2p) reactions on nuclei 6Li, 7Li, 12C and 40Ca. In this experiment, polarizations of the secondary protons from the (p, 2p) reactions are measured using 1 GeV proton beam of the PNPI synchrocyclotron. Two final protons from the reaction are detected in coincidence by means of a two-arm magnetic spectrometer at non-symmetric scattering angles. The resolution of the spectrometer on separation energy of 4.5 MeV (FWHM) is enough to distinguish reliably the shell structure of the investigated nuclei. In order to measure polarization of the two secondary protons, both spectrometer arms are equipped with multiwire proportional chamber polarimeters.Strong reduction of polarizations (large depolarization factor) relatively to free pp scattering is observed in the experiment. The 6Li, 7Li P-shell data are interpreted in terms of this reduction being combined with classical phenomenon of the effective polarization calculated with the help of DWIA.For the S-shell protons the depolarization factors are apparently seen not being obscured by the spin-orbit coupling. In case of the 7Li S-shell data the depolarization factors calculated by deviation from IA are found to be ΔP/P=0.31±0.07 and 0.39±0.04 for the scattered and recoil proton polarization, respectively. As estimations show, significant and roughly equal polarization reduction of the two secondary protons with essentially different energies (≈-200 and 800 MeV) can hardly be explained by a trivial nuclear distortion effect like depolarization due to rescatterings in nuclear matter. Measurements with heavier nucleus targets (12C, 40Ca) show that magnitude of the depolarization is a decreasing function of the nuclear density in the part of the nucleus volume which effectively contributes to the pp scattering in a nucleus. An explanation of the observed depolarization might be done in terms of modification of the pp-scattering amplitude in the nuclear meidum.
118619470
Prospects for B Physics Measurements using the CMS Detector at the LHC
The LHC provides new opportunities to improve our understanding of the b quark using high statistics data samples and the 14 TeV center-of-mass energy. The prospects to measure the cross section for inclusive b production in events containing jets and at least one muon are presented. Additionally, the feasibility for CMS to measure the mass and the lifetime of the BBc meson and to search for the rare leptonic decay BsB →μμ are presented. Detailed studies of detector systematic effects and theoretical uncertainties are included Presented at XXXIII International Conference on High Energy Physics (ICHEP) July 26 August 2, 2006 Moscow
21384151
Aligning the CMS muon endcap detector with a system of optical sensors
The positions and orientations of one sixth of 468 large cathode strip chambers in the endcaps of the CMS muon detector are directly monitored by several hundred sensors including 2-D optical sensors with linear CCDs illuminated by cross-hair lasers. Position measurements obtained by photo- grammetry and survey under field-off conditions show that chambers in the +Z endcap have been placed on the yoke disks with an average accuracy of about plusmn1 mm in all 3 dimensions. We reconstruct absolute Zciws-positions and orientations of chambers at B=0T and B=4T using data from the optical alignment system. The measured position resolution and sensitivity to relative motion is ~60 mum. The precision for measuring chamber positions taking into account mechanical tolerances is ~270 mum. Comparing reconstruction of optical alignment data and photogrammetry measurements at B=0T indicates an accuracy of ~ 680 mum currently achieved with the hardware alignment system. Optical position measurements at B=4T show significant chamber displacements of up to 13 mm due to yoke disk deformation.
197518814
Heavy flavor production in gamma gamma collisions
124722292
Volume-based Representation of the Magnetic Field
The access to the magnetic field has a large impact on both CPU performance and accuracy of simulation, reconstruction and analysis software. An approach to the magnetic field access based on a volume geometry is described. The volumes are constructed in such a way that their boundaries correspond to field discontinuities, which are due to changes in magnetic permeability of the materials. The field in each volume is continuous. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when it is available, from a parameterization. To allow global access to the magnetic field, a volume finding algorithm that exploits explicitly the layout and the symmetries of the detector is used. The main clients of the magnetic field, which are the simulation (GEANT) and the propagation of track parameters and errors in the reconstruction, can be made aware of the magnetic field volumes by connecting the per-volume magnetic field providers to the corresponding volume in the respective geometries. In this way the global volume search is by-passed and the access to the field is sped up significantly.