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15 results on '"Hommez B"'

1. Quark helicity distributions in the nucleon for up, down, and strange quarks from semi-inclusive deep-inelastic scattering

Author

Airapetian, A., Akopov, N., Avetissian, E., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C. A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Bailey, P., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W. D., Oganessyan, K., Ohsuga, H., Pickert, N., Potashov, S., Potterveld, D. H., Baturin, V., Raithel, M., Reggiani, D., Reimer, P. E., Reischl, A., Reolon, A. R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Baumgarten, C., Rubin, J., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K. P., Beckmann, M., Schwind, A., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T. A., Shutov, V., Simani, M. C., Sinram, K., Belostotski, S., Stancari, M., Statera, M., Steffens, E., Steijger, J. J. M., Stenzel, H., Stewart, J., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Bernreuther, S., Tchuiko, B., Terkulov, A., Tkabladze, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., Vetterli, M. C., Vikhrov, V., Bianchi, N., Vincter, M. G., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Ybeles Smit, G., Yen, S., Zihlmann, B., Blok, H. P., Zohrabian, H., Zupranski, P., HERMES Collaboration, Blumlein, J., Akopov, Z., Bottcher, H., Borissov, A., Borysenko, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G. P., Chiang, H. C., Ciullo, G., Amarian, M., Contalbrigo, M., Dalpiaz, P. F., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Ammosov, V. V., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Andrus, A., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Aschenauer, E. C., Grebeniouk, O., Greeniaus, L. G., Gregor, I. M., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W. H. A., Augustyniak, W., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H. E., Jgoun, A., Kaiser, R., Avakian, R., Kinney, E., Kisselev, A., Konigsmann, K., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V. G., Lagamba, L., Lapikas, Louk, Avetissian, A., Laziev, A., Lenisa, P., Liebing, P., Lindemann, T., Linden-Levy, L. A., Lipka, K., Lorenzon, W., Lu, J., Maiheu, B., Makins, N. C. R., (Astro)-Particles Physics, Photo Conversion Materials, and Student Lab and Education

Subjects
Quark, internal [polarized target], Nuclear and High Energy Physics, Particle physics, Strange quark, sea [quark], High Energy Physics::Lattice, deep inelastic scattering [positron deuteron], Hadron, Nuclear Theory, dependence [flavor], Down quark, FOS: Physical sciences, HERMES, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), density [helicity], 27.5 GeV, Pion, 0103 physical sciences, ddc:530, SDG 14 - Life Below Water, deep inelastic scattering [positron p], 010306 general physics, electroproduction [pi], Physics, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, polarization [quark], Deep inelastic scattering, moment, Baryon, DESY HERA Stor, electroproduction [K], Up quark, valence [quark], polarization [cross section], High Energy Physics::Experiment, polarized beam [positron], asymmetry [spin], experimental results
Abstract

Polarized deep-inelastic scattering data on longitudinally polarized hydrogen and deuterium targets have been used to determine double-spin asymmetries of cross sections. Inclusive and semi-inclusive asymmetries for the production of positive and negative pions from hydrogen were obtained in a reanalysis of previously published data. Inclusive and semi-inclusive asymmetries for the production of negative and positive pions and kaons were measured on a polarized deuterium target. The separate helicity densities for the up and down quarks and the anti-up, anti-down, and strange sea quarks were computed from these asymmetries in a "leading order" QCD analysis. The polarization of the up-quark is positive and that of the down-quark is negative. All extracted sea quark polarizations are consistent with zero, and the light quark sea helicity densities are flavor symmetric within the experimental uncertainties. First and second moments of the extracted quark helicity densities in the measured range are consistent with fits of inclusive data. © 2005 The American Physical Society.

Published
2005
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2. Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target

Author

Airapetian, A., Akopov, N., Bacchetta, A., Mikloukho, O., Miller, C. A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W. D., Bailey, P., Oganessyan, K., Ohsuga, H., Osborne, A., Pickert, N., Potterveld, D. H., Raithel, M., Reggiani, D., Reimer, P. E., Reischl, A., Reolon, A. R., Balin, D., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Rubin, J., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, Igor A., Beckmann, M., Schafer, A., Schill, C., Schnell, G., Schuler, K. P., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T. A., Belostotski, S., Shutov, V., Sinram, K., Sommer, W., Stancari, M., Statera, M., Steffens, E., Steijger, J. J. M., Stenzel, H., Stewart, J., Stinzing, F., Bianchi, N., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P. B., van der Steenhoven, G., Blok, H. P., van Haarlem, Y., Vetterli, M. C., Vikhrov, V., Vincter, M. G., Vogel, C., Volmer, J., Wang, S., Wendland, J., Wilbert, J., Ybeles Smit, G., Bottcher, H., Ye, Y., Ye, Z., Yen, S., Zihlmann, B., Zupranski, P., HERMES Collaboration, Borissov, A., Borysenko, A., Akopov, Z., Bouwhuis, M., Brull, A., Bryzgalov, V., Capitani, G. P., Cappiluppi, M., Chen, T., Ciullo, G., Contalbrigo, M., Dalpiaz, P. F., De Leo, R., Amarian, M., Demey, M., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Andrus, A., Elschenbroich, U., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Aschenauer, E. C., Gavrilov, G., Gharibyan, V., Grebeniouk, O., Gregor, I. M., Hadjidakis, C., Hafidi, K., Hartig, M., Hasch, D., Henoch, M., Hesselink, W. H. A., Augustyniak, W., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Hristova, I., Iarygin, G., Ilyichev, A., Ivanilov, A., Izotov, A., Jackson, H. E., Avakian, R., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Kobayashi, T., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V. G., Avetissian, A., Lagamba, L., Lapikas, Louk, Laziev, A., Lenisa, P., Liebing, P., Linden-Levy, L. A., Lorenzon, W., Lu, H., Lu, J., Lu, S., Avetissian, E., Ma, B. Q., Maiheu, B., Makins, N. C. R., Mao, Y., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Michler, T., (Astro)-Particles Physics, Photo Conversion Materials, and Student Lab and Education

Subjects
Particle physics, transverse [polarization], Nuclear Theory, FOS: Physical sciences, General Physics and Astronomy, HERMES, 13.60.–r, Inelastic scattering, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), 27.5 GeV, Pion, 13.88.+e, ddc:550, Vector meson, SDG 14 - Life Below Water, deep inelastic scattering [positron p], 14.20.Dh, 14.65.–q, Nuclear Experiment, Physics, Scattering, polarized target [hydrogen], High Energy Physics::Phenomenology, polarization [quark], Deep inelastic scattering, +pi+positron+anything%22">positron p --> pi positron anything, angular dependence, DESY HERA Stor, Distribution function, High Energy Physics::Experiment, transverse momentum [quark], Nucleon, electroproduction [pi+], asymmetry [spin], electroproduction [pi-], Lepton, experimental results
Abstract

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 ($\ensuremath{\phi}$) and the target spin axis (${\ensuremath{\phi}}_{S}$) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component $\mathbf{⟨}\mathrm{sin} (\ensuremath{\phi}+{\ensuremath{\phi}}_{S}){\mathbf{⟩}}_{UT}^{\ensuremath{\pi}}$ is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component $\mathbf{⟨}\mathrm{sin} (\ensuremath{\phi}\ensuremath{-}{\ensuremath{\phi}}_{S}{\mathbf{⟩}}_{UT}^{\ensuremath{\pi}}$ arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.

Published
2005
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3. Nuclear polarization of molecular hydrogen recombined on a non-metallic surface

Author

Airapetian, A, Akopov, N, Akopov, Z, Amarian, M, Ammosov, Vv, Andrus, A, Aschenauer, Ec, Augustymak, W, Avakian, R, Avetissian, A, Avetissian, E, Bailey, P, Baturin, V, Baumgarten, C, Beckmann, M, Belostotski, S, Bernreuther, S, Bianchi, N, Blok, Hp, Bottcher, H, Borissov, A, Borysenko, A, Bouwhuis, M, Brack, J, Brull, A, Bryzgalov, V, Capitanilo, Gp, Chiang, Hc, Ciullo, Giuseppe, Contalbrigo, Marco, Court, G, Ferretti, Paola, DE LEO, R, DE NARDO, L, DE SANCTIS, E, Devitsin, E, DI NEZZA, P, Duren, M, Ehrenfried, M, ELALAOUI MOULAY, A, Elbakian, G, Ellinghaus, F, Elschenbroich, U, Ely, J, Fabbri, Riccardo, Fantoni, A, Fechtchenko, A, Felawka, L, Fox, B, Franz, J, Frullani, S, Gapienko, G, Gapienko, V, Garibaldi, F, Garrow, K, Garutti, E, Gaskell, D, Gavrilov, G, Gharibyan, V, Graw, G, Grebeniouk, O, Greeniaus, Lg, Gregor, Im, Haeberli, W, Hafidi, K, Hartig, M, Hasch, D, Heesbeen, D, Henoch, M, Hertenberger, R, Hesselink, Wha, Hillenbrand, A, Hoek, M, Holler, Y, Hommez, B, Iarygin, G, Ivanilov, A, Izotov, A, Jackson, He, Jgoun, A, Kaiser, R, Kinney, E, Kisselev, A, Kolster, H, Konigsmann, K, Kopytin, M, Korotkov, V, Kozlov, V, Krauss, B, Krivokhijine, Vg, Lagamba, L, Lapikas, L, Laziev, A, Lenisa, Paolo, Liebing, P, LINDEN LEVY LA, Lipka, K, Lorenzon, W, Lu, J, Maiheu, B, Makins, Ncr, Marianski, B, Marukyan, H, Masoli, Francesco Antonio, Mexner, V, Meyners, N, Mikloukho, O, Miller, Ca, Miyachi, Y, Muccifora, V, Nagaitsev, A, Nappi, E, Naryshkin, Y, Nass, A, Negodaev, M, Nowak, Wd, Oganessyan, K, Ohsuga, H, Pickert, N, Potashov, S, Potterveld, Dh, Raithel, M, Reggiani, Davide, Reimer, Pe, Reischl, A, Reolon, Ar, Riedl, C, Rith, K, Rosner, G, Rostomyan, A, Rubacek, L, Rubin, J, Ryckbosch, D, Salomatin, Y, Sanjiev, I, Savin, I, Scarlett, C, Schill, C, Schnell, G, Schuler, Kp, Schwind, A, Seele, J, Seidl, R, Seitz, B, Shanidze, R, Shearer, C, Shibata, Ta, Shutov, V, Simani, Mc, Sinram, K, Stancari, Michelle Dawn, Statera, Marco, Steffens, E, Steijger, Jjm, Stenzel, H, Stewart, J, Stosslein, U, Tait, P, Tanaka, H, Taroian, S, Tchuiko, B, Terkulov, A, Tkabladze, A, Trzcinski, A, Tytgat, M, Vandenbroucke, A, VAN DER NAT, P, VAN DER STEENHOVEN, G, Vetterli, Mc, Vikhrov, V, Vincter, Mg, Vogel, C, Vogt, M, (Astro)-Particles Physics, Photo Conversion Materials, Student Lab and Education, and Airapetian, A

Subjects
Silicon, Atomic Physics (physics.atom-ph), media_common.quotation_subject, Nuclear Theory, chemistry.chemical_element, FOS: Physical sciences, Asymmetry, Physics - Atomic Physics, Metal, Physics - Chemical Physics, 29.25.Pj - Polarized and other targets, 34. - Atomic and molecular collision processes and interactions, 39.10.+j - Atomic and molecular beam sources and techniques, 13.88.+e - Polarization in interactions and scattering, Molecule, Nuclear Experiment, media_common, chemistry.chemical_classification, Physics, Chemical Physics (physics.chem-ph), Scattering, Polymer, Polarization (waves), Atomic and Molecular Physics, and Optics, chemistry, visual_art, visual_art.visual_art_medium, Atomic physics, Recombination
Abstract

The nuclear polarization of $\mathrm{H}_2$ molecules formed by recombination of nuclear polarized H atoms on the surface of a storage cell initially coated with a silicon-based polymer has been measured by using the longitudinal double-spin asymmetry in deep-inelastic positron-proton scattering. The molecules are found to have a substantial nuclear polarization, which is evidence that initially polarized atoms retain their nuclear polarization when absorbed on this type of surface

Published
2004
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4. Flavor decomposition of the sea quark helicity distributions in the nucleon from semiinclusive deep inelastic scattering

Author

Airapetian, A., Akopov, N., Avetissian, E., Mexner, V., Meyners, N., Mikloukho, O., Miller, C. A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Bailey, P., Negodaev, M., Nowak, W.-D., Oganessyan, K., Ohsuga, H., Orlandi, G., Pickert, N., Potashov, S., Potterveld, D. H., Raithel, M., Reggiani, D., Baturin, V., Reimer, P. E., Reischl, A., Reolon, A. R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Ryckbosch, D., Salomatin, Y., Baumgarten, C., Sanjiev, I., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K. P., Schwind, A., Seele, J., Seidl, R., Beckmann, M., Seitz, B., Shanidze, R., Shearer, C., Shibata, T.-A., Shutov, V., Simani, M. C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Belostotski, S., Steijger, J. J. M., Stewart, J., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Tkabladze, A., Trzcinski, A., Bernreuther, S., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., Vetterli, M. C., Vikhrov, V., Vincter, M. G., Visser, J., Vogel, C., Vogt, M., Bianchi, N., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Ybeles Smit, G., Yen, S., Zihlmann, B., Zohrabian, H., Zupranski, P., HERMES Collaboration, Blok, H. P., Bottcher, H., Akopov, Z., Borissov, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G. P., Chiang, H. C., Ciullo, G., Contalbrigo, M., Dalpiaz, P. F., Amarian, M., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Ammosov, V. V., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Frullani, S., Garber, Y., Andrus, A., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Aschenauer, E. C., Greeniaus, L. G., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W. H. A., Hillenbrand, A., Hoek, M., Augustyniak, W., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H. E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Avakian, R., Konigsmann, K., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V. G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Avetissian, A., Liebing, P., Lindemann, T., Lipka, K., Lorenzon, W., Lu, J., Maiheu, B., Makins, N. C. R., Marianski, B., Marukyan, H., and Masoli, F.

Subjects
sea [quark], momentum spectrum [quark], High Energy Physics::Lattice, deep inelastic scattering [positron deuteron], Nuclear Theory, HERMES, absorption [photon], x-dependence, inclusive reaction [positron deuteron], helicity [quark], ddc:550, Nuclear Experiment, 27.6 GeV, High Energy Physics::Phenomenology, DESY HERA Stor, electroproduction [K+], electroproduction [K-], flavor [quark], High Energy Physics::Experiment, asymmetry [flavor], polarized beam [positron], polarized target [deuteron], electroproduction [pi+], asymmetry [spin], electroproduction [pi-], experimental results
Abstract

Double-spin asymmetries of semi-inclusive 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 re-analyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.

Published
2004
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5. Evidence for a narrow |S|=1 baryon state at a mass of 1528 MeV in quasi-real photoproduction

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Balin, D., Baturin, V., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Borysenko, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G.P., Chen, T., Chen, X., Chiang, H.C., Ciullo, G., Contalbrigo, M., Dalpiaz, P.F., Deconinck, W., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, Y., Garrow, K., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Gregor, I.M., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Liebing, P., Linden-Levy, L.A., Lipka, K., Lorenzon, W., Lu, H., Lu, J., Lu, S., Lu, X., Ma, B.Q., Maiheu, B., Makins, N.C.R., Mao, Y., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W.D., Oganessyan, K., Ohsuga, H., Pickert, N., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reischl, A., Reolon, A.R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Rubin, J., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Schafer, A., Schill, C., Schnell, G., Schuler, K.P., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T.A., Shutov, V., Simani, M.C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stenzel, H., Stewart, J., Stinzing, F., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terklov, A., Tkabladze, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Smit, G.Y., Ye, Y., Ye, Z., Yen, Z., Yu, W., Zihlmann, B., Zohrabian, H., and Zupranski, P.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, QC
Abstract

Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK(S)(0) → ppi(+)pi(-). A peak is observed in the pK(S)(0) invariant mass spectrum at 1528 +/- 2.6(stat) +/- 2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4-6 standard deviations and its width may be somewhat larger than the experimental resolution of sigma = 4.3-6.2 MeV. This state may be interpreted as the predicted S = +1 exotic Theta(+)(uudd (s) over bar) pentaquark baryon. No signal for an hypothetical Theta(++) baryon was observed in the pK(+) invariant mass distribution. The absence of such a signal indicates that an isotensor Theta is excluded and an isovector Theta is unlikely.

Published
2004

6. Hard exclusive electroproduction of π+π-pairs

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Balin, D., Baturin, V., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Borysenko, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G.P., Chen, T., Ciullo, G., Contalbrigo, M., Dalpiaz, P.F., De Leo, R., Demey, M., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Garutti, E., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Gregor, I.M., Griffioen, K.A., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Liebing, P., Linden-Levy, L.A., Lipka, K., Lorenzon, W., Lu, H., Lu, J., Lu, S., Ma, B.Q., Maiheu, B., Makins, N.C.R., Mao, Y., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W.D., Oganessyan, K., Ohsuga, H., Osborne, A., Pickert, N., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reischl, A., Reolon, A.R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Rubin, J., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Schafer, A., Schill, C., Schnell, G., Schuler, K., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T., Shutov, V., Sinram, K, Sommer, W., Stancari, M., Statera, M., Steffens, E., Steijger, J.J., Stenzel, H., Stewart, J., Stinzing, F., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Tkabladze, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., van Haarlem, Y., Vetterli, M., Vikhrov, V., Vincter, M., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Smit, G., Ye, Y, Ye, Z, Yen, S, Zihlmann, B, and Zupranski, P.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, QC
Abstract

Hard exclusive electroproduction of pi(+) pi(-) pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY Legendre moments (P-1) and (P-3) of the angular distributions of pi(+) mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the pi(+) pi(-) invariant mass can be understood as being due to the interference between relative P-wave (isovector) and S-, D-wave (isoscalar) states of the two pions. The increase in magnitude of (P-1) as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq exchange for larger values of x, which leads to a sizable admixture of isoscalar and isovector pion pairs. In addition, the interference between P-wave and D-wave states separately for transverse and longitudinal pion pairs has been studied. The data indicate that in the f(2)(1270) region at [Q(2)] = 3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component.

Published
2004

7. Double-spin asymmetries in the cross section of rho /sup 0/ and phi production at intermediate energies

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Baturin, V., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G.P., Chiang, H.C., Ciullo, G., Contalbrigo, M., Court, G.R., Dalpiaz, P.F., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Frullani, S., Garber, Y., Gapienko, G., Gapienko, V., Garibaldi, F., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Haeberli, W., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Konigsmann, K., Kolster, H., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Liebing, P., Lindemann, T., Lipka, K., Lorenzon, W., Maiheu, B., Makins, N.C.R., Marianski, B., Marukyan, H., Masoli, F., Menden, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Nowak, W.D., Oganessyan, K., Ohsuga, H., Orlandi, G., Pickert, N., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P., Reischl, A., Reolon, A.R., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K.P., Schwind, A., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T.A., Shutov, V., Simani, M.C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stewart, J., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Thomas, E., Tkabladze, A., Trzcinski, A., Tytgat, M., Urciuoli, G.M., van der Nat, P., van der Steenhoven, G., Van de Vyver, R., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Visser, J., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Wise, T., Yen, S., Yoneyama, S., Zihlmann, B., Zohrabian, H., and Zupranski, P.

Subjects
High Energy Physics::Phenomenology, Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, QC
Abstract

Double-spin asymmetries in the cross section of electroproduction of rho /sup 0/ and phi mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive rho /sup 0/ electroproduction on the proton exhibits a positive tendency. This is consistent with theoretical predictions that the exchange of an object with unnatural parity contributes to exclusive rho /sup 0/ electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in rho /sup 0/ and phi meson electroproduction by quasireal photons were also found to be consistent with zero; the asymmetry in the case of the phi meson is compatible with a theoretical prediction which involves ss knockout from the nucleon.

Published
2003

8. Quark fragmentation to pi(+/-), pi(0), K-+/-, p and (p)over-bar in the nuclear environment

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Baturin, V., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Borysenko, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G.P., Chiang, H.C., Ciullo, G., Contalbrigo, M., Dalpiaz, P.F., De Leo, R., De Nardo, L., De Santis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Gregor, I.M., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Konigsmann, K., Kopytin, M., Laziev, A., Lenisa, P., Liebing, P., Lindemann, T., Lipka, K., Lorenzon, W., Lu, J., Maiheu, B., Makins, N.C.R., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W.D., Oganessyan, K., Ohsuga, H., Pickert, N., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reischl, A., Reolon, A.R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K.P., Schwind, A., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T.A., Shutov, V., Simani, M.C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stenzel, H., Stewart, J., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Tkabladze, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Smit, G.Y., Yen, S., Zihlmann, B., Zohrabian, H., and Zupranski, P.

Subjects
High Energy Physics::Phenomenology, Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, QC
Abstract

The influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi- inclusive deep-inelastic scattering of 27.6 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity for krypton relative to that of deuterium has been measured for the first time for various identified hadrons (pi(+), pi(-), pi(0), K+, K-, p and (p) over bar) as a function of the virtual photon energy v, the fraction z of this energy transferred to the hadron, and the hadron transverse momentum squared p(t)(2). The multiplicity ratio is strongly reduced in the nuclear medium at low v and high z, with significant differences among the various hadrons. The distribution of the hadron transverse momentum is broadened towards high p(t)(2) in the nuclear medium, in a manner resembling the Cronin effect previously observed in collisions of heavy ions and protons with nuclei.

Published
2003

9. The Q(2)-dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron, proton and neutron

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Aschenauer, E.C., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Baturin, V., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Bouhali, O., Bouwhuis, M., Brack, J., Brauksiepe, S., Brull, A., Brunn, I., Capitani, G.P., Chiang, H.C., Ciullo, G., Court, G.R., Dalpiaz, P.F., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fischer, H., Fox, B., Franz, J., Frullani, S., Garber, Y., Gapienko, G., Gapienko, V., Garibaldi, F., Garutti, E., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Green, P.W., Greeniaus, L.G., Gute, A., Haeberli, W., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Heinsius, F.H., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Holler, Y., Hommez, B., Iarygin, G., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R, Kinney, E., Kisselev, A., Kitching, P., Konigsmann, K., Kolster, H., Kopytin, M., Korotkov, V., Kotik, E., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Liebing, P., Lindemann, T., Lipka, K., Lorenzon, W., Makins, N.C.R., Marukyan, H., Masoli, F., Menden, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Nowak, W.D., Oganessyan, K., Ohsuga, H., Orlandi, G., Podiatchev, S., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reisch, A., Reolon, A.R., Rith, K., Rosner, G., Rostomyan, A., Ryckbosch, D., Sanjiev, I., Sato, F., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K.P., Schwind, A., Seibert, J., Seitz, B., Shanidze, R., Shibata, T.A., Shutov, V., Simani, M.C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stewart, J., Stosslein, U., Suetsugu, K., Tanaka, H., Taroian, S., Terkulov, A., Teryaev, O., Tessarin, S., Thomas, E., Tkabladze, A., Tytgat, M., Urciuoli, G.M., van der Nat, P., van der Steenhoven, G., Van de Vyver, R., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Visser, J., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Wise, T., Yen, S., Yoneyama, S., Zihlmann, B., Zohrabian, H., and Zupranski, P.

Subjects
Nuclear Theory, Nuclear Experiment, QC
Abstract

The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity- dependent photoabsorption cross sections. Originally conceived for real photons, the GDH integral can be generalised to the case of photons with virtuality Q(2). For spin-1/2 targets such as the nucleon, it then represents the non-perturbative limit of the first moment Gamma(1) of the spin structure function g(1)(x,Q(2)) in deep inelastic scattering (DIS). The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides an unprecedented and complete measurement of the generalised GDH integral for photon-virtuality ranging over 1.2 lt Q(2) lt 12.0 GeV2 and for photon-nucleon invariant mass squared W-2 ranging over I lt W2 lt 45 GeV2. thus covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. These data allow the study of the Q(2)- dependence of the full GDH integral, which is sensitive to both the Q(2)-evolution of the resonance form factors and contributions of higher twist. The contribution of the nucleon- resonance region is seen to decrease rapidly with increasing Q(2). The DIS contribution is sizeable over the full measured range, even down to the lowest measured Q(2). As expected, at higher Q(2) the data are found to be in agreement with previous measurements of the first moment of g(1). From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton-neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at Q(2) = 5 GeV2.

Published
2003

10. Q(2) dependence of nuclear transparency for exclusive rho(0) production

Author

AIRAPETIAN, A, AKOPOV, N, AKOPOV, Z, Elschenbroich, U., Hommez, B., Ryckbosch, Dirk, Schnell, Gunar, Tytgat, Michael, and van de Vyver, R.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, Science General
Abstract

Exclusive coherent and incoherent electroproduction of the rho(0) meson from H-1 and N-14 targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q(2)). The ratio of N-14 to H-1 cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q(2) is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency.

Published
2003

11. Evidence for quark-hadron duality in the proton spin asymmetry A(1)

Author

AIRAPETIAN, A, AKOPOV, N, AKOPOV, Z, Elschenbroich, U., Hommez, B., Ryckbosch, Dirk, Tytgat, Michael, and van de Vyver, R.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, Science General
Abstract

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A(1). Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q(2) between 1.2 and 12 GeV2 and values of W-2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A(1) in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q(2) above 1.6 GeV2.

Published
2003

12. Double-spin asymmetries in the cross section of rho(0) and phi production at intermediate energies

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V. V., Andrus, A., Aschenauer, E. C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Baturin, V., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H. P., Bottcher, H., Borissov, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G. P., Chiang, H. C., Ciullo, Giuseppe, Contalbrigo, Marco, Court, G. R., Ferretti, Paola, De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Ely, J., Fabbri, Riccardo, Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Frullani, S., Garber, Y., Gapienko, G., Gapienko, V., Garibaldi, F., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L. G., Haeberli, W., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W. H. A., Hillenbrand, A., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H. E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Konigsmann, Kay C., Kolster, H., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V. G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, Paolo, Liebing, P., Lindemann, T., Lipka, K., Lorenzon, W., Maiheu, B., Makins, N. C. R., Marianski, B., Marukyan, H., Masoli, Francesco Antonio, Menden, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C. A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Nowak, W. D., Oganessyan, K., Ohsuga, H., Orlandi, G., Pickert, N., Potashov, S., Potterveld, D. H., Raithel, M., Reggiani, Davide, Reimer, P., Reischl, A., Reolon, A. R., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, Igor A., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K. P., Schwind, A., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T. A., Shutov, V., Simani, M. C., Sinram, K., Stancari, Michelle Dawn, Statera, Marco, Steffens, E., Steijger, J. J. M., Stewart, J., Stosslein, U., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Thomas, E., Tkabladze, A., Trzcinski, A., Tytgat, M., Urciuoli, G. M., van der Nat, P., van der Steenhoven, G., van de Vyver, R., Vetterli, M. C., Vikhrov, V., Vincter, M. G., Visser, J., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Wise, T., Yen, S., Yoneyama, S., Zihlmann, B., Zohrabian, H., Zupranski, P., and (Astro)-Particles Physics

Subjects
HERMES experiment, Particle physics, Photon, Physics and Astronomy (miscellaneous), Meson, media_common.quotation_subject, Nuclear Theory, rho(770) electroproduction, electron p inelastic scattering, electron deuteron inelastic scattering, electron polarized beam, polarized target, Phi(1020) electroproduction, spin asymmetry, x-dependence, momentum transfer dependence, transverse momentum dependence, quark strangeness, quark sea, pomeron exchange, magnetic spectrometer, HERMES experimental results, DESY HERA Stored 27.5 GeV, 01 natural sciences, 7. Clean energy, Asymmetry, High Energy Physics - Experiment, 0103 physical sciences, 010306 general physics, Nuclear Experiment, Engineering (miscellaneous), media_common, Physics, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, Parity (physics), 3. Good health, Deuterium, High Energy Physics::Experiment, Nucleon
Abstract

Double-spin asymmetries in the cross section of electroproduction of $\rho^0$ and $\phi$ mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive $\rho^0$ electroproduction on the proton exhibits a positive tendency. This is consistent with theoretical predictions that the exchange of an object with unnatural parity contributes to exclusive $\rho^0$ electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in $\rho^0$ and $\phi $ meson electroproduction by quasi-real photons were also found to be consistent with zero; the asymmetry in the case of the $\phi$ meson is compatible with a theoretical prediction which involves $s\bar{s}$ knockout from the nucleon., Comment: 8 pages, 7 figures

Published
2003
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13. Measurement of single-spin azimuthal asymmetries in semi-inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, H., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Baturin, V., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Bottcher, H., Borissov, A., Bouwhuis, M., Brack, J., Brull, A., Bryzgalov, V., Capitani, G.P., Chiang, H.C., Ciullo, G., Contalbrigo, M., Court, G.R., Dalpiaz, P.F., De Leo, R., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Duren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Eischenbroich, U., Ely, J., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Fox, B., Franz, J., Frullani, S., Garber, Y., Gapienko, G., Gapienko, V., Garibaldi, F., Garutti, E., Gaskell, D., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Haeberli, W., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Konigsmann, K., Kolster, H., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikas, L., Laziev, A., Lenisa, P., Liebing, P., Lindemann, T, Lipka, K., Lorenzon, W., Ma, B., Makins, N.C.R., Marukyan, H., Masoli, F., Menden, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Nowak, W.D., Oganessyan, K., Ohsuga, H., Orlandi, G., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reischl, A., Reolon, A.R., Rith, K., Rosner, G., Rostomyan, A., Ryckbosch, D., Sanjiev, I., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schnell, G., Schuler, K.P., Schwind, A., Seidl, R., Seibert, J., Seitz, B., Shanidze, R., Shibata, T., Shutov, V., Simani, M.C., Sinram, K., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stewart, J., Stosslein, U., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Tessarin, S., Thomas, E., Tkabladze, A., Trzcinski, A., Tytgat, A., Urciuoli, G.M., van der Nat, P., van der Steenhoven, G., Van de Vyver, R., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Visser, J., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Wise, T., Yen, S., Yoneyama, S., Zihlmann, B., Zohrabian, H., Zupranski, P., Photo Conversion Materials, (Astro)-Particles Physics, and Student Lab and Education

Subjects
Nuclear and High Energy Physics, Particle physics, Meson, Nuclear Theory, Hadron, Virtual particle, FOS: Physical sciences, 01 natural sciences, High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), Pion, 13.88.+e, 0103 physical sciences, 010306 general physics, Nuclear Experiment, QC, Spin-½, 13.60.-r, Physics, 010308 nuclear & particles physics, Scattering, High Energy Physics::Phenomenology, Deuterium, 13.87.Fh, 14.20.Dh, Condensed Matter::Strongly Correlated Electrons, High Energy Physics::Experiment, Astrophysics::Earth and Planetary Astrophysics, SDG 6 - Clean Water and Sanitation, Lepton
Abstract

Single-spin asymmetries have been measured for semi-inclusive electroproduction of $\pi^+$, $\pi^-$, $\pi^0$ and $K^+$ mesons in deep-inelastic scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle $\phi$ around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the $\sin \phi$ moment of the cross section are $0.012 \pm 0.002 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^+$, $0.006 \pm 0.003 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^-$, $0.021 \pm 0.005 {(stat.)} \pm 0.003 {(syst.)}$ for $\pi^0$ and $0.013 \pm 0.006 {(stat.)} \pm 0.003 {(syst.)}$ for $K^+$. The $\sin 2\phi$ moments are compatible with zero for all particles., Comment: Revised version shortened 9 pages, 3 tables, 7 figures

Published
2002
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14. Hadron formation in deep-inelastic positron scattering in a nuclear environment

Author

Airapetian, A., Akopov, N., Akopov, Z., Akushevich, I., Amarian, T., Arrington, J., Aschenauer, E.C., Avakian, H., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Bains, B., Baumgarten, C., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Bottcher, H., Borissov, A., Bouwhuis, M., Brack, J., Brauksiepe, S., Braun, B., Bruckner, W., Brull, A., Budz, P., Bulten, H.J., Capitani, G.P., Carter, P., Chumney, P., Cisbani, E., Court, G.R., Dalpiaz, P.F., De Leo, R., De Nardo, L., De Sanctis, E., De Schepper, D., Devitsin, E., Witt Huberts, P.K.A., Di Nezza, P., Djordadze, V., Duren, M., Dvoredsky, A., Elbakian, G., Ely, J., Fantoni, A., Fechtchenko, A., Felawka, L., Ferro-Luzzi, M, Fiedler, K., Filippone, B.W., Fischer, H., Fox, B., Franz, J., Frullani, S., Garber, Y., Garibaldi, F., Garutti, E., Gavrilov, G., Gharibyan, V., Golendukhin, A., Graw, G., Grebeniouk, O., Green, P.W., Greeniaus, L.G., Gute, A., Haeberli, W., Hartig, M., Hasch, D., Heesbeen, D., Heinsius, F.H., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hofman, G., Holer, Y., Holt, R.J., Hommez, B., Iarygin, G., Iodice, M., Izotov, A., Jackson, H.E., Jgoun, A., Jung, P., Kaiser, R., Kanesaka, J., Kinnev, E., Kisselev, A., Kitching, P., Koch, N., Konigsmann, K., Kolster, H., Korotkov, V., Kotik, E., Kozlov, V., Krivokhijine, V.G., Kyle, G., Lagamba, L., Laziev, A., Lenisa, P., Lindemann, T., Lorenzon, W., Makins, N.C.R., Martin, J.W., Marukyan, H., Masoli, F., McAndrew, M., McIlhany, K., Mckeown, R.D., Meissner, F., Menden, F., Metz, A., Meyners, N., Mikloukho, O., Miller, C.A., Milner, R., Muccifora, V., Mussa, R., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaeva, K., Nowak, W.D., Oganessyan, K., O'Neill, T.G., Openshaw, R., Ouyang, J., Owen, B.R., Pate, S.F., Potashov, S., Potterveld, D.H., Rakness, G., Rappoport, V., Redwine, R., Reggiani, D., Reolon, A.R., Ristinen, R., Rith, K., Robinson, D., Rostomyan, A., Ruh, M., Ryckbosch, D., Sakemi, Y., Sato, T., Savin, I., Scarlett, C., Schafer, A., Schill, C., Schmidt, F., Schnell, G., Schuler, K., Schwind, A., Seibert, J., Seitz, B., Shibata, T.A., Shin, T., Shutov, V., Simani, M.C., Simon, A., Sinram, K., Steffens, E., Steijger, J.J.M., Stewart, J., Stosslein, U., Suetsugu, K., Sutter, M., Taroian, S., Terklov, A., Tessarin, S., Thomas, E., Tipton, B., Tytgat, M., Urciuoli, G.M., van den Brand, J.F.J., van der Stennhoven, G., Van de Vyver, R., van Hunen, J.J., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Visser, J., Volk, E., Weiskopf, C., Wendland, J., Wilbert, J., Wise, T., Yen, S., Yoneyama, S., and Zohrabian, H.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment, QC
Abstract

The influence of the nuclear medium on the production of charged hadrons in semi-inclusive deep-inelastic scattering has been studied by the HERMES experiment at DESY using a 27.5 GeV positron beam. The differential multiplicity of charged hadrons and identified charged pions from nitrogen relative to that from deuterium has been measured as a function of the virtual photon energy nu and the fraction z of this energy transferred to the hadron. There are observed substantial reductions of the multiplicity ratio R/sub M//sup h/ at low nu and at high z, both of which are well described by a gluon-bremsstrahlung model of hadronization. A significant difference of the nu -dependence of R/sub M//sup h/ is found between positive and negative hadrons. This is interpreted in terms of a difference between the formation times of protons and pions, using a phenomenological model to describe the nu - and z-dependence of R/sub M//sup h/.

Published
2001

15. Hard exclusive electroproduction of π+π− pairs

Author

Airapetian, A., Akopov, N., Akopov, Z., Amarian, M., Ammosov, V.V., Andrus, A., Aschenauer, E.C., Augustyniak, W., Avakian, R., Avetissian, A., Avetissian, E., Bailey, P., Balin, D., Baturin, V., Beckmann, M., Belostotski, S., Bernreuther, S., Bianchi, N., Blok, H.P., Böttcher, H., Borissov, A., Borysenko, A., Bouwhuis, M., Brack, J., Brüll, A., Bryzgalov, V., Capitani, G.P., Chen, T., Ciullo, G., Contalbrigo, M., Dalpiaz, P.F., De Leo, R., Demey, M., De Nardo, L., De Sanctis, E., Devitsin, E., Di Nezza, P., Düren, M., Ehrenfried, M., Elalaoui-Moulay, A., Elbakian, G., Ellinghaus, F., Elschenbroich, U., Fabbri, R., Fantoni, A., Fechtchenko, A., Felawka, L., Frullani, S., Gapienko, G., Gapienko, V., Garibaldi, F., Garrow, K., Garutti, E., Gavrilov, G., Gharibyan, V., Graw, G., Grebeniouk, O., Greeniaus, L.G., Gregor, I.M., Griffioen, K.A., Hafidi, K., Hartig, M., Hasch, D., Heesbeen, D., Henoch, M., Hertenberger, R., Hesselink, W.H.A., Hillenbrand, A., Hoek, M., Holler, Y., Hommez, B., Iarygin, G., Ivanilov, A., Izotov, A., Jackson, H.E., Jgoun, A., Kaiser, R., Kinney, E., Kisselev, A., Kopytin, M., Korotkov, V., Kozlov, V., Krauss, B., Krivokhijine, V.G., Lagamba, L., Lapikás, L., Laziev, A., Lenisa, P., Liebing, P., Linden-Levy, L.A., Lipka, K., Lorenzon, W., Lu, H., Lu, J., Lu, S., Ma, B.-Q., Maiheu, B., Makins, N.C.R., Mao, Y., Marianski, B., Marukyan, H., Masoli, F., Mexner, V., Meyners, N., Mikloukho, O., Miller, C.A., Miyachi, Y., Muccifora, V., Nagaitsev, A., Nappi, E., Naryshkin, Y., Nass, A., Negodaev, M., Nowak, W.-D., Oganessyan, K., Ohsuga, H., Osborne, A., Pickert, N., Potashov, S., Potterveld, D.H., Raithel, M., Reggiani, D., Reimer, P.E., Reischl, A., Reolon, A.R., Riedl, C., Rith, K., Rosner, G., Rostomyan, A., Rubacek, L., Rubin, J., Ryckbosch, D., Salomatin, Y., Sanjiev, I., Savin, I., Schäfer, A., Schill, C., Schnell, G., Schüler, K.P., Seele, J., Seidl, R., Seitz, B., Shanidze, R., Shearer, C., Shibata, T.-A., Shutov, V., Sinram, K., Sommer, W., Stancari, M., Statera, M., Steffens, E., Steijger, J.J.M., Stenzel, H., Stewart, J., Stinzing, F., Tait, P., Tanaka, H., Taroian, S., Tchuiko, B., Terkulov, A., Tkabladze, A., Trzcinski, A., Tytgat, M., Vandenbroucke, A., van der Nat, P., van der Steenhoven, G., van Haarlem, Y., Vetterli, M.C., Vikhrov, V., Vincter, M.G., Vogel, C., Vogt, M., Volmer, J., Weiskopf, C., Wendland, J., Wilbert, J., Ybeles Smit, G., Ye, Y., Ye, Z., Yen, S., Zihlmann, B., and Zupranski, P.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment
Abstract

Hard exclusive electroproduction of π+π− pairs off hydrogen and deuterium targets has been studied by the HERMES experiment at DESY. Legendre moments 〈P1〉 and 〈P3〉 of the angular distributions of π+ mesons in the center-of-mass frame of the pair have been measured for the first time. Their dependence on the π+π− invariant mass can be understood as being due to the interference between relative P-wave (isovector) and S-, D-wave (isoscalar) states of the two pions. The increase in magnitude of 〈P1〉 as Bjorken x increases is interpreted in the framework of generalized parton distributions as an enhancement of flavour non-singlet qq¯ exchange for larger values of x, which leads to a sizable admixture of isoscalar and isovector pion pairs. In addition, the interference between P-wave and D-wave states separately for transverse and longitudinal pion pairs has been studied. The data indicate that in the f2(1270) region at 〈Q2〉=3 GeV2 higher-twist effects can be as large as the leading-twist longitudinal component.

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