Deeply virtual and exclusive electroproduction of ω-mesons

L. Morand, D. Doré, M. Garçon, M. Guidal, J. M. Laget, S. Morrow, F. Sabatié, E. Smith, G. Adams, P. Ambrozewicz, M. Anghinolfi, G. Asryan, G. Audit, H. Avakian, H. Bagdasaryan, J. Ball, J. P. Ball, N. A. Baltzell, S. Barrow, V. BatourineM. Battaglieri, M. Bektasoglu, M. Bellis, N. Benmouna, B. L. Berman, A. S. Biselli, S. Boiarinov, B. E. Bonner, S. Bouchigny, R. Bradford, D. Branford, W. J. Briscoe, W. K. Brooks, S. Bültmann, V. D. Burkert, C. Butuceanu, J. R. Calarco, S. L. Careccia, D. S. Carman, A. Cazes, S. Chen, P. L. Cole, D. Cords, P. Corvisiero, D. Crabb, J. P. Cummings, E. de Sanctis, R. DeVita, P. V. Degtyarenko, H. Denizli, L. Dennis, A. Deur, K. V. Dharmawardane, K. S. Dhuga, C. Djalali, G. E. Dodge, J. Donnelly, D. Doughty, Michael Dugger, S. Dytman, O. P. Dzyubak, H. Egiyan, K. S. Egiyan, L. Elouadrhiri, P. Eugenio, R. Fatemi, G. Feldman, R. G. Fersch, R. J. Feuerbach, H. Funsten, G. Gavalian, G. P. Gilfoyle, K. L. Giovanetti, F. X. Girod, J. T. Goetz, C. I O Gordon, R. W. Gothe, K. A. Griffioen, M. Guillo, N. Guler, L. Guo, V. Gyurjyan, C. Hadjidakis, R. S. Hakobyan, J. Hardie, D. Heddle, F. W. Hersman, K. Hicks, I. Hleiqawi, M. Holtrop, C. E. Hyde-Wright, Y. Ilieva, D. G. Ireland, M. M. Ito, D. Jenkins, H. S. Jo, K. Joo, H. G. Juengst, J. D. Kellie, M. Khandaker, W. Kim, A. Klein, F. J. Klein, A. V. Klimenko, M. Kossov, V. Kubarovski, L. H. Kramer, S. E. Kuhn, J. Kuhn, J. Lachniet, J. Langheinrich, D. Lawrence, T. Lee, L. Ji, K. Livingston, C. Marchand, L. C. Maximon, S. McAleer, B. McKinnon, J. W C McNabb, B. A. Mecking, S. Mehrabyan, J. J. Melone, M. D. Mestayer, C. A. Meyer, K. Mikhailov, R. Minehart, M. Mirazita, R. Miskimen, V. Mokeev, J. Mueller, G. S. Mutchler, J. Napolitano, R. Nasseripour, S. Niccolai, G. Niculescu, I. Niculescu, B. B. Niczyporuk, R. A. Niyazov, M. Nozar, G. V. O'Rielly, M. Osipenko, A. I. Ostrovidov, K. Park, E. Pasyuk, S. A. Philips, N. Pivnyuk, D. Pocanic, O. Pogorelko, E. Polli, I. Popa, S. Pozdniakov, B. M. Preedom, J. W. Price, Y. Prok, D. Protopopescu, B. A. Raue, G. Riccardi, G. Ricco, M. Ripani, Barry Ritchie, F. Ronchetti, G. Rosner, P. Rossi, P. D. Rubin, C. Salgado, J. P. Santoro, V. Sapunenko, R. A. Schumacher, V. S. Serov, Y. G. Sharabian, J. Shaw, A. V. Skabelin, L. C. Smith, D. I. Sober, A. Stavinsky, S. Stepanyan, S. S. Stepanyan, B. E. Stokes, P. Stoler, I. I. Strakovsky, S. Strauch, M. Taiuti, D. J. Tedeschi, U. Thoma, A. Tkabladze, L. Todor, C. Tur, M. Ungaro, M. F. Vineyard, A. V. Vlassov, L. B. Weinstein, D. P. Weygand, M. Williams, E. Wolin, M. H. Wood, A. Yegneswaran, L. Zana

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Abstract

The exclusive ω electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross-sections were measured up to large values of the four-momentum transfer (- t < 2.7 GeV2) to the proton. The contributions of the interference terms σTT and σTL to the cross-sections, as well as an analysis of the ω spin density matrix, indicate that helicity is not conserved in this process. The t-channel π0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction γ* p → ωp, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross-sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.

Original languageEnglish (US)
Pages (from-to)445-458
Number of pages14
JournalEuropean Physical Journal A
Volume24
Issue number3
DOIs
StatePublished - Jun 2005

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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