Erhard Steffens

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Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton(More)
Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the ρ(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q < 4 GeV and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the Hermes spectrometer, using a longitudinally(More)
A. Airapetian p, N. Akopov aa, Z. Akopov aa, A. Andrus o, E.C. Aschenauer g, W. Augustyniak z, R. Avakian aa, A. Avetissian aa, E. Avetissian k, S. Belostotski s, N. Bianchi k, H.P. Blok r,y, H. Böttcher g, C. Bonomo j, A. Borissov n, A. Brüll 1, V. Bryzgalov t, J. Burns n, M. Capiluppi j, G.P. Capitani k, E. Cisbani v, G. Ciullo j, M. Contalbrigo j, P.F.(More)
The CLIC damping ring requires wigglers with both high on-axis fields and short periods. The present design foresees a superconductive wiggler with a period length of 5 cm, a peak on-axis field of 2.5 T and a full aperture of 12 mm. In this paper we explore the performance improvements of the damping ring when these parameters are pushed to 2.7 T at a(More)
A. Airapetian, N. Akopov, Z. Akopov, M. Amarian, 32 V.V. Ammosov, A. Andrus, E.C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetissian, P. Bailey, V. Baturin, C. Baumgarten, M. Beckmann, S. Belostotski, S. Bernreuther, N. Bianchi, H.P. Blok, 30 H. Böttcher, A. Borissov, M. Bouwhuis, J. Brack, A. Brüll, I. Brunn, G.P. Capitani, H.C. Chiang,(More)
Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for(More)
K. Ackerstaff, A. Airapetian, N. Akopov, I. Akushevich M. Amarian, E.C. Aschenauer, H. Avakian, R. Avakian, A. Avetissian, B. Bains, C. Baumgarten, M. Beckmann, St. Belostotski, J.E. Belz, Th. Benisch, S. Bernreuther, N. Bianchi, J. Blouw, H. Böttcher, A. Borissov, J. Brack, S. Brauksiepe, B. Braun, B. Bray, St. Brons, W. Brückner, A. Brüll, E.E.W. Bruins,(More)
A. Airapetian,32 N. Akopov,32 M. Amarian,24,27,32 E. C. Aschenauer,13,14,6 H. Avakian,10 R. Avakian,32 A. Avetissian,32 E. Avetissian,10,32 B. Bains,15 C. Baumgarten,22 M. Beckmann,12 S. Belostotski,25 J. E. Belz,28,29 Th. Benisch,8 S. Bernreuther,8 N. Bianchi,10 J. Blouw,24 H. Böttcher,6 A. Borissov,6,14 M. Bouwhuis,15 J. Brack,4 S. Brauksiepe,12 B.(More)
V. Koptev,1 M. Büscher,2 H. Junghans,2 M. Nekipelov,1,2 K. Sistemich,2 H. Ströher,2 V. Abaev,1 H.-H. Adam,3 R. Baldauf,4 S. Barsov,1 U. Bechstedt,2 N. Bongers,2 G. Borchert,2 W. Borgs,2 W. Bräutigam,2 W. Cassing,5 V. Chernyshev,6 B. Chiladze,7 M. Debowski,8 J. Dietrich,2 M. Drochner,4 S. Dymov,9 J. Ernst,10 W. Erven,4 R. Esser,11,* P. Fedorets,6 A.(More)
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the HERMES spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of(More)