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Search Results: 1 - 10 of 297143 matches for " D. v. 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.
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.
Realtime calibration of the A4 electromagnetic lead fluoride calorimeter
S. Baunack,D. Balaguer Ríos,L. Capozza,J. Diefenbach,R. Frascaria,B. Gl?ser,D. v. Harrach,Y. Imai,R. Kothe,R. Kunne,J. H. Lee,F. E. Maas,M. C. Mora Espí,M. Morlet,S. Ong,E. Schilling,J. van de Wiele,C. Weinrich
Physics , 2011, DOI: 10.1016/j.nima.2011.02.099
Abstract: Sufficient energy resolution is the key issue for the calorimetry in particle and nuclear physics. The calorimeter of the A4 parity violation experiment at MAMI is a segmented calorimeter where the energy of an event is determined by summing the signals of neighbouring channels. In this case the precise matching of the individual modules is crucial to obtain a good energy resolution. We have developped a calibration procedure for our total absorbing electromagnetic calorimeter which consists of 1022 lead fluoride (PbF_2) crystals. This procedure reconstructs the the single-module contributions to the events by solving a linear system of equations, involving the inversion of a 1022 x 1022-matrix. The system has shown its functionality at beam energies between 300 and 1500 MeV and represents a new and fast method to keep the calorimeter permanently in a well-calibrated state.
Electron Scattering with Polarized Targets at TESLA
The TESLA-N Study Group,:,M. Anselmino,E. C. Aschenauer,S. Belostotski,W. Bialowons,J. Bluemlein,V. Braun,R. Brinkmann,M. Dueren,F. Ellinghaus,K. Goeke,St. Goertz,A. Gute,J. Harmsen,D. v. Harrach,R. Jakob,E. M. Kabuss,R. Kaiser,V. Korotkov,P. Kroll,E. Leader,B. Lehmann-Dronke,L. Mankiewicz,A. Meier,W. Meyer,N. Meyners,D. Mueller,P. J. Mulders,W. -D. Nowak,L. Niedermeier,K. Oganessyan,P. V. Pobilitsa,M. V. Polyakov,G. Reicherz,K. Rith,D. Ryckbosch,A. Schaefer,K. Sinram,G. v. d. Steenhoven,E. Steffens,J. Steijger,C. Weiss
Physics , 2000,
Abstract: Measurements of polarized electron-nucleon scattering can be realized at the TESLA linear collider facility with projected luminosities that are about two orders of magnitude higher than those expected of other experiments at comparable energies. Longitudinally polarized electrons, accelerated as a small fraction of the total current in the e+ arm of TESLA, can be directed onto a solid state target that may be either longitudinally or transversely polarized. A large variety of polarized parton distribution and fragmentation functions can be determined with unprecedented accuracy, many of them for the first time. A main goal of the experiment is the precise measurement of the x- and Q^2-dependence of the experimentally totally unknown quark transversity distributions that will complete the information on the nucleon's quark spin structure as relevant for high energy processes. Comparing their Q^2-evolution to that of the corresponding helicity distributions constitutes an important precision test of the predictive power of QCD in the spin sector. Measuring transversity distributions and tensor charges allows access to the hitherto unmeasured chirally odd operators in QCD which are of great importance to understand the role of chiral symmetry. The possibilities of using unpolarized targets and of experiments with a real photon beam turn TESLA-N into a versatile next-generation facility at the intersection of particle and nuclear physics.
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
S. Baunack,K. Aulenbacher,D. Balaguer Ríos,L. Capozza,J. Diefenbach,B. Gl?ser,D. v. Harrach,Y. Imai,E. M. Kabu?,R. Kothe,J. H. Lee,H. Merkel,M. C. Mora Espí,U. Müller,E. Schilling,G. Stephan,C. Weinrich,J. Arvieux,M. A. El-Yakoubi,R. Kunne,F. E. Maas,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,Y. Prok,S. Taylor
Physics , 2009, DOI: 10.1103/PhysRevLett.102.151803
Abstract: A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q^2=0.22 (GeV/c)^2 is reported here. The measured asymmetry is A_LR=(-17.23 +- 0.82_stat +-0.89_syst) ppm. The Standard Model prediction assuming no strangeness is A_0=(-15.87 +- 1.22) ppm. In combination with previous results from measurements at forward angles, it it possible to disentangle for the first time the strange electric and magnetic form factors at this momentum transfer, G_E^s(0.22)=0.050 +- 0.038 +- 0.019 and G_M^s(0.22)=-0.14 +- 0.11 +- 0.11.
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.
Enhancing residual-based techniques with shape reconstruction features in Electrical Impedance Tomography
Bastian Harrach,Mach Nguyet Minh
Mathematics , 2015,
Abstract: In electrical impedance tomography, algorithms based on minimizing a linearized residual functional have been widely used due to their flexibility and good performance in practice. However, no rigorous convergence results have been available in the literature yet, and reconstructions tend to contain ringing artifacts. In this work, we shall minimize the linearized residual functional under a linear constraint defined by a monotonicity test, which plays a role of a special regularizer. Global convergence is then established to guarantee that this method is stable under the effects of noise. Moreover, numerical results show that this method yields good shape reconstructions under high levels of noise without appearance of artifacts.
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