Spin density matrix elements in exclusive ρ 0 electroproduction on 1H and 2H targets at 27.5 GeV beam energy

A. Airapetian, N. Akopov, Z. Akopov, A. Andrus, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetissian, S. Belostotski, N. Bianchi, H. P. Blok, H. Böttcher, C. Bonomo, A. Borissov, A. Brüll, V. Bryzgalov, M. Capiluppi, G. P. Capitani, E. CisbaniG. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, M. Demey, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, J. Dreschler, M. Düren, M. Ehrenfried, A. Elalaoui-Moulay, G. Elbakian, F. Ellinghaus, U. Elschenbroich, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, A. Funel, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, O. Grebeniouk, I. M. Gregor, H. Guler, C. Hadjidakis, M. Hartig, D. Hasch, T. Hasegawa, W. H.A. Hesselink, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, B. Hommez, I. Hristova, G. Iarygin, Y. Imazu, A. Ivanilov, A. Izotov, H. E. Jackson, A. Jgoun, R. Kaiser, T. Keri, E. Kinney, A. Kisselev, T. Kobayashi, M. Kopytin, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, R. Lamb, L. Lapikás, I. Lehmann, P. Lenisa, P. Liebing, L. A. Linden-Levy, W. Lorenzon, S. Lu, X. R. Lu, B. Q. Ma, B. Maiheu, N. C.R. Makins, S. I. Manaenkov, Y. Mao, B. Marianski, H. Marukyan, V. Mexner, C. A. Miller, Y. Miyachi, V. Muccifora, M. Murray, A. Mussgiller, A. Nagaitsev, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. D. Nowak, A. Osborne, L. L. Pappalardo, R. Perez-Benito, N. Pickert, M. Raithel, D. Reggiani, P. E. Reimer, A. Reischl, A. R. Reolon, C. Riedl, K. Rith, S. E. Rock, G. Rosner, A. Rostomyan, L. Rubacek, J. Rubin, D. Ryckbosch, Y. Salomatin, I. Sanjiev, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, C. Shearer, T. A. Shibata, V. Shutov, M. Stancari, M. Statera, J. E. Steffens, J. J.M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, J. Streit, P. Tait, S. Taroian, B. Tchuiko, A. Terkulov, A. Trzcinski, M. Tytgat, A. Vandenbroucke, P. B. Van Der Nat, G. Van Der Steenhoven, Y. Van Haarlem, C. Van Hulse, M. Varanda, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, H. Ye, Y. Ye, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, P. Zupranski

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44 Scopus citations

Abstract

Spin Density Matrix Elements (SDMEs) describing the angular distribution of exclusive ρ 0 electroproduction and decay are determined in the HERMES experiment with 27.6 GeV beam energy and unpolarized hydrogen and deuterium targets. Eight (fifteen) SDMEs that are related (unrelated) to the longitudinal polarization of the beam are extracted in the kinematic region 1<Q 2<7 GeV2, 3.0<W<6.3 GeV, and -t<0.4 GeV2. Within the given experimental uncertainties, a hierarchy of relative sizes of helicity amplitudes is observed. Kinematic dependences of all SDMEs on Q 2 and t are presented, as well as the longitudinal-to- transverse ρ 0 electroproduction cross-section ratio as a function of Q 2. A small but statistically significant deviation from the hypothesis of s-channel helicity conservation is observed. An indication is seen of a contribution of unnatural-parity-exchange amplitudes; these amplitudes are naturally generated with a quark-exchange mechanism.

Original languageEnglish (US)
Pages (from-to)659-695
Number of pages37
JournalEuropean Physical Journal C
Volume62
Issue number4
DOIs
StatePublished - Aug 2009
Externally publishedYes

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Physics and Astronomy (miscellaneous)

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