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Search Results: 1 - 10 of 195482 matches for " D. von Harrach "
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Lambda and Lambda-bar Polarization in Lepton Induced Processes
A. Kotzinian,A. Bravar,D. von Harrach
Physics , 1997, DOI: 10.1007/s100520050142
Abstract: The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. Current and future semi-inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish between various models for the spin transfer mechanisms.
Gluon polarization from correlated high-pT hadron pairs in polarized electro-production
A. Bravar,D. von Harrach,A. Kotzinian
Physics , 1997, DOI: 10.1016/S0370-2693(97)01578-5
Abstract: We propose to measure the gluon distribution function Delta G(eta) at eta < 0.2 via pseudo jet production in polarized fixed target lepton nucleon scattering at typical lepton beam energies of 200 GeV. The measurement of the spin-asymmetry for the production of correlated charge conjugated hadrons of opposite transverse momentum can be directly related to Delta G(eta) through the photo-gluon fusion process. Wa also present a numerical analysis of the accuracy which can be obtained for different flavors and kinematics of the observed hadron pair.
Gluon Polarization from Correlated High-p_T Hadron Pairs in Polarized l - N Scattering
A. Bravar,D. von Harrach,A. Kotzinian
Physics , 1997, DOI: 10.1063/1.53683
Abstract: We propose to access the gluon polarization $\Delta G$ by measuring the cross section spin-asymmetry in semi-inclusive polarized lepton -- nucleon scattering. The photon-gluon fusion sub-process will be tagged by detecting high-$p_T$ correlated hadron pairs in the forward hemisphere. Selecting oppositely charged kaon pairs will allow to suppress the background coming from gluon radiation.
Theory Meets Experiment for the Determination of $ΔG/G$
D. von Harrach,W. -D. Nowak,J. Soffer
Physics , 1997,
Abstract: We briefly summarize the main points made during the discussion session on the determination of $\Delta G/G$, where all Workshop participants were strongly encouraged to contribute.
Measurements and simulations of Cherenkov light in lead fluoride crystals
P. Achenbach,S. Baunack,K. Grimm,T. Hammel,D. von Harrach,A. Lopes Ginja,F. E. Maas,E. Schilling,H. Stroeher
Physics , 2001, DOI: 10.1016/S0168-9002(01)00668-4
Abstract: The anticipated use of more than one thousand lead fluoride (PbF2) crystals as a fast and compact Cherenkov calorimeter material in a parity violation experiment at MAMI stimulated the investigation of the light yield (L.Y.) of these crystals. The number of photoelectrons (p.e.) per MeV deposited energy has been determined with a hybrid photomultiplier tube (HPMT). In response to radioactive sources a L.Y. between 1.7 and 1.9 p.e./MeV was measured with 4% statistical and 5% systematic error. The L.Y. optimization with appropriate wrappings and couplings was investigated by means of the HPMT. Furthermore, a fast Monte Carlo simulation based on the GEANT code was employed to calculate the characteristics of Cherenkov light in the PbF2 crystals. The computing time was reduced by a factor of 50 compared to the regular photon tracking method by implementing detection probabilities as a three-dimensional look-up table. For a single crystal a L.Y. of 2.1 p.e./MeV was calculated. The corresponding detector response to electrons between 10 and 1000 MeV was highly linear with a variation smaller than 1%.
Research Paper Polyclonal antibodies production against Staphylococcus aureus protein A: ELISA technique optimization for milk quality control
Y Belkessam, M Benali, S Moulessehoul, D Harrach
African Journal of Biotechnology , 2010,
Abstract: The main aim of this project is to produce polyclonal antibodies directed against the Staphylococcus aureus protein A and their use to appreciate bacteriological analysis of milk quality. In this context, an immunization produce was set up to test and detect in a batch of animals the convenient responder to the injected antigen. Furthermore, to optimize all parameters of retained ELISA test, a cross-table was conceived by using various concentrations of different reagents and has allowed selecting the optimal dilutions as follows: 1) 1/1000 for anti-Staphylococcus aureus protein A mouse antibodies and 1/2000 for anti-Staphylococcus aureus protein A rabbit antibodies. 2) 1/4000 for anti-Staphylococcus aureus treated by heat mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. 3) 1/2000 for anti-Staphylococcus aureus treated by NaClO mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. The application of optimized ELISA test to search and detect Staphylococcus aureus germs in different samples of milk has shown very satisfying results when compared to those obtained by bacteriological method. Indeed, the sensitiveness and the reproducibility, as well as the possibility to analyze a great number of samples in the same time at a reduced manner make the immunochemical method a best choice of test able to replace recent bacteriological methods.
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabub,R. Kothe,J. H. Lee,A. Sanchez-Lorente,E. Schilling,D. Schwaab,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. Elyakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. Vandewiele,S. Kowalski,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.082001
Abstract: We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A$_\perp$, at two Q$^2$ values of \qsquaredaveragedlow (GeV/c)$^2$ and \qsquaredaveragedhighII (GeV/c)$^2$ and a scattering angle of $30^\circ < \theta_e < 40^\circ$. The measured transverse asymmetries are A$_{\perp}$(Q$^2$ = \qsquaredaveragedlow (GeV/c)$^2$) = (\experimentalasymmetry alulowcorr $\pm$ \statisticalerrorlow$_{\rm stat}$ $\pm$ \combinedsyspolerrorlowalucor$_{\rm sys}$) $\times$ 10$^{-6}$ and A$_{\perp}$(Q$^2$ = \qsquaredaveragedhighII (GeV/c)$^2$) = (\experimentalasymme tryaluhighcorr $\pm$ \statisticalerrorhigh$_{\rm stat}$ $\pm$ \combinedsyspolerrorhighalucor$_{\rm sys}$) $\times$ 10$^{-6}$. The first errors denotes the statistical error and the second the systematic uncertainties. A$_\perp$ arises from the imaginary part of the two-photon exchange amplitude and is zero in the one-photon exchange approximation. From comparison with theoretical estimates of A$_\perp$ we conclude that $\pi$N-intermediate states give a substantial contribution to the imaginary part of the two-photon amplitude. The contribution from the ground state proton to the imaginary part of the two-photon exchange can be neglected. There is no obvious reason why this should be different for the real part of the two-photon amplitude, which enters into the radiative corrections for the Rosenbluth separation measurements of the electric form factor of the proton.
Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2
A4 Collaboration,F. E. Maas,P. Achenbach,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,K. Grimm,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabuss,R. Kothe,J. H. Lee,A. Lorente,A. Lopes Ginja,L. Nungesser,E. Schilling,G. Stephan,C. Weinrich,I. Altarev,J. Arvieux,B. Collin,R. Frascaria,M. Guidal,R. Kunne,D. Marchand,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,B. Plaster,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.93.022002
Abstract: We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a $Q^2$ of 0.230 (GeV/c)^2 and a scattering angle of \theta_e = 30^o - 40^o. Using a large acceptance fast PbF_2 calorimeter with a solid angle of \Delta\Omega = 0.62 sr the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A_{phys} =(-5.44 +- 0.54_{stat} +- 0.27_{\rm sys}) 10^{-6}. The Standard Model expectation assuming no strangeness contributions to the vector form factors is $A_0=(-6.30 +- 0.43) 10^{-6}$. The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G^s_E + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2 = 0.032 +- 0.028.
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at $Q^2$ = 0.108 (GeV/c)$^2$
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,T. Hammel,D. von Harrach,Y. Imai,E. -M. Kabu?,R. Kothe,J. H. Lee,A. Lorente,E. Schilling,D. Schwaab,M. Sikora,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. El-Yakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,B. Plaster,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.152001
Abstract: We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of $Q^2$ = \Qsquare (GeV/c)$^2$ and at a forward electron scattering angle of 30$^\circ < \theta_e < 40^\circ$. The measured asymmetry is $A_{LR}(\vec{e}p)$ = (\Aphys $\pm$ \Deltastat$_{stat}$ $\pm$ \Deltasyst$_{syst}$) $\times$ 10$^{-6}$. The expectation from the Standard Model assuming no strangeness contribution to the vector current is A$_0$ = (\Azero $\pm$ \DeltaAzero) $\times$ 10$^{-6}$. We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher $Q^2$. We have extracted the strangeness contribution to the electromagnetic form factors from our data to be $G_E^s$ + \FakGMs $G_M^s$ = \GEsGMs $\pm $ \DeltaGEsGMs at $Q^2$ = \Qsquare (GeV/c)$^2$. As in our previous measurement at higher momentum transfer for $G_E^s$ + 0.230 $G_M^s$, we again find the value for $G_E^s$ + \FakGMs $G_M^s$ to be positive, this time at an improved significance level of 2 $\sigma$.
Pattern recognition and PID for COMPASS RICH-1
P. Abbon,M. Alexeev,H. Angerer,R. Birsa,P. Bordalo,F. Bradamante,A. Bressan,M. Chiosso,P. Ciliberti,M. L. Colantoni,T. Dafni,S. Dalla Torre,E. Delagnes,O. Denisov,H. Deschamps,V. Diaz,N. Dibiase,V. Duic,W. Eyrich,A. Ferrero,M. Finger,M. Finger Jr,H. Fischer,S. Gerassimov,M. Giorgi,B. Gobbo,R. Hagemann,D. von Harrach,F. H. Heinsius,R. Joosten,B. Ketzer,V. N. Kolosov,K. K?nigsmann,I. Konorov,D. Kramer,F. Kunne,A. Lehmann,S. Levorato,A. Maggiora,A. Magnon,A. Mann,A. Martin,G. Menon,A. Mutter,O. N?hle,F. Nerling,D. Neyret,D. Panzieri,S. Paul,G. Pesaro,C. Pizzolotto,J. Polak,P. Rebourgeard,F. Robinet,E. Rocco,P. Schiavon,C. Schill,P. Schoenmeier,W. Schr?der,L. Silva,M. Slunecka,F. Sozzi,L. Steiger,M. Sulc,M. Svec,S. Takekawa,F. Tessarotto,A. Teufel,H. Wollny
Physics , 2009, DOI: 10.1016/j.nima.2008.07.015
Abstract: A package for pattern recognition and PID by COMPASS RICH-1 has been developed and used for the analysis of COMPASS data collected in the years 2002 to 2004, and 2006-2007 with the upgraded RICH-1 photon detectors. It has allowed the full characterization of the detector in the starting version and in the upgraded one, as well as the PID for physics results. We report about the package structure and algorithms, and the detector characterization and PID results.
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