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Search Results: 1 - 10 of 507604 matches for " E. M. Kabuss "
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A high power liquid hydrogen target for the Mainz A4 parity violation experiment
I. Altarev,E. Schilling,S. Baunack,L. Capozza,J. Diefenbach,K. Grimm,Th. Hammel,D. vonHarrach,Y. Imai,E. M. Kabuss,R. Kothe,J. H. Lee,A. LopesGinja,F. E. Maas,A. SanchezLorente,G. Stephan,C. Weinrich
Physics , 2005, DOI: 10.1016/j.nima.2006.03.022
Abstract: We present a new powerful liquid hydrogen target developed for the precise study of parity violating electron scattering on hydrogen and deuterium. This target has been designed to have minimal target density fluctuations under the heat load of a 20$\mu$A CW 854.3 MeV electron beam without rastering the electron beam. The target cell has a wide aperture for scattered electrons and is axially symmetric around the beam axis. The construction is optimized to intensify heat exchange by a transverse turbulent mixing in the hydrogen stream, which is directed along the electron beam. The target is constructed as a closed loop circulating system cooled by a helium refrigerator. It is operated by a tangential mechanical pump with an optional natural convection mode. The cooling system supports up to 250 watts of the beam heating removal. Deeply subcooled liquid hydrogen is used for keeping the in-beam temperature below the boiling point. The target density fluctuations are found to be at the level 10$^{-3}$ at a beam current of 20 $\mu$A.
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.
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.
Results on the nucleon spin structure
Eva-Maria Kabuss
Physics , 1999, DOI: 10.1007/s10582-999-0095-3
Abstract: SMC performed an investigation of the spin structure of the nucleon by measuring deep inelastic scattering of polarised muons off polarised protons and deuterons. A summary of the results for spin structure functions and sum rules is given.
COMPASS - a facility to study QCD
Eva-Maria Kabuss
Physics , 2011,
Abstract: An overview on the new COMPASS II experimental programme is presented. The main topics include a study of Primakoff reactions, generalised parton distributions via deeply virtual Compton scattering and transverse momentum dependent distributions in Drell-Yan processes in the pion scattering off polarised protons. Moreover, the studies of semi-inclusive deep inelastic scattering on unpolarised target will be continued.
Asymmetries from Semi-inclusive Polarized Deep Inelastic Scattering
Eva-Maria Kabuss
Physics , 1997, DOI: 10.1063/1.53728
Abstract: The analysis of semi-inclusive data from deep inelastic scattering of polarized muons off polarized protons and deuterons by the SMC is presented. The resulting charged hadron asymmetries are used to determine polarized valence and sea quark distributions and their contributions to the nucleon spin. In addition, a new approach to derive inclusive asymmetries is discussed.
Final results from the NMC
Eva-Maria Kabuss
Physics , 1997, DOI: 10.1063/1.53714
Abstract: A summary of the results on deep inelastic muon nucleon and muon nucleus scattering experiments performed by the NMC collaboration is presented.
Future Polarised DIS Fixed Target Experiments
Eva-Maria Kabuss
Physics , 1999, DOI: 10.1016/S0920-5632(99)00793-8
Abstract: New experiments in polarised deep inelastic scattering will mainly concentrate on the measurement of semi-inclusive asymmetries. Especially, the upgraded HERMES experiment at DESY and the newly build COMPASS experiment at CERN will investigate the gluon polarisation via open charm and high p_T hadron pair production, study in detail the flavour decomposition of the quark helicity distributions and measure the tranversity distributions with tranversely polarised targets.
Induced surface enhancement in coral Pt island films attached to nanostructured Ag electrodes
H. K. Ly,Ch. K?hler,A. Fischer,J. Kabuss,F. Schlosser,M. Schoth,A. Knorr,I. M. Weidinger
Physics , 2012,
Abstract: Coral Pt islands films are deposited via electrochemical reduction on silica coated nanostructured Ag electrodes. From these devices surface enhanced (resonance) Raman [SE(R)R] signals of molecules exclusively attached to Pt are obtained with intensities up to 50% of the value determined for Ag. SE(R)R spectroscopic investigations are carried out with different probe molecules, silica coating thicknesses and excitation lines. Additionally, field enhancement calculations on Ag-SiO2-Pt support geometries are performed to elucidate the influence of the Pt island film nanostructure on the observed Raman intensities. It is concluded that the non perfect coating of the Pt island film promotes the efficiency of the induced Pt SER activity. Comparison with similar measurements on Ag-SiO2-Au electrodes further suggests that the chemical nature of the deposited metal island film plays a minor role for the SE(R)R intensity.
A luminosity monitor for the A4 parity violation experiment at MAMI
T. Hammel,P. Achenbach,S. Baunack,L. Capozza,J. Diefenbach,K. Grimm,D. vonHarrach,Y. Imai,E. Kabuss,R. Kothe,J. H. Lee,A. LopesGinja,F. E. Maas,A. SanchezLorente,E. Schilling,G. Stephan,C. Weinrich,I. Altarev
Physics , 2005, DOI: 10.1016/j.nima.2006.03.028
Abstract: A water Cherenkov luminosity monitor system with associated electronics has been developed for the A4 parity violation experiment at MAMI. The detector system measures the luminosity of the hydrogen target hit by the MAMI electron beam and monitors the stability of the liquid hydrogen target. Both is required for the precise study of the count rate asymmetries in the scattering of longitudinally polarized electrons on unpolarized protons. Any helicity correlated fluctuation of the target density leads to false asymmetries. The performance of the luminosity monitor, investigated in about 2000 hours with electron beam, and the results of its application in the A4 experiment are presented.
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