European Physical Journal C: Particles and Fields (Apr 2011)

Ratios of helicity amplitudes for exclusive ρ0 electroproduction

  • The HERMES Collaboration,
  • A. Airapetian,
  • N. Akopov,
  • Z. Akopov,
  • E. C. Aschenauer,
  • W. Augustyniak,
  • R. Avakian,
  • A. Avetissian,
  • E. Avetisyan,
  • S. Belostotski,
  • N. Bianchi,
  • H. P. Blok,
  • A. Borissov,
  • J. Bowles,
  • V. Bryzgalov,
  • J. Burns,
  • M. Capiluppi,
  • G. P. Capitani,
  • E. Cisbani,
  • G. Ciullo,
  • M. Contalbrigo,
  • P. F. Dalpiaz,
  • W. Deconinck,
  • R. De Leo,
  • L. De Nardo,
  • E. De Sanctis,
  • M. Diefenthaler,
  • P. Di Nezza,
  • M. Düren,
  • M. Ehrenfried,
  • G. Elbakian,
  • F. Ellinghaus,
  • R. Fabbri,
  • A. Fantoni,
  • L. Felawka,
  • S. Frullani,
  • D. Gabbert,
  • G. Gapienko,
  • V. Gapienko,
  • F. Garibaldi,
  • G. Gavrilov,
  • V. Gharibyan,
  • F. Giordano,
  • S. Gliske,
  • M. Golembiovskaya,
  • C. Hadjidakis,
  • M. Hartig,
  • D. Hasch,
  • G. Hill,
  • A. Hillenbrand,
  • M. Hoek,
  • Y. Holler,
  • I. Hristova,
  • Y. Imazu,
  • A. Ivanilov,
  • H. E. Jackson,
  • H. S. Jo,
  • S. Joosten,
  • R. Kaiser,
  • G. Karyan,
  • T. Keri,
  • E. Kinney,
  • A. Kisselev,
  • N. Kobayashi,
  • V. Korotkov,
  • V. Kozlov,
  • P. Kravchenko,
  • V. G. Krivokhijine,
  • L. Lagamba,
  • R. Lamb,
  • L. Lapikás,
  • I. Lehmann,
  • P. Lenisa,
  • L. A. Linden-Levy,
  • A. López Ruiz,
  • W. Lorenzon,
  • X.-G. Lu,
  • X.-R. Lu,
  • B.-Q. Ma,
  • D. Mahon,
  • N. C. R. Makins,
  • S. I. Manaenkov,
  • L. Manfré,
  • Y. Mao,
  • B. Marianski,
  • A. Martinez de la Ossa,
  • H. Marukyan,
  • C. A. Miller,
  • Y. Miyachi,
  • A. Movsisyan,
  • V. Muccifora,
  • M. Murray,
  • A. Mussgiller,
  • E. Nappi,
  • Y. Naryshkin,
  • A. Nass,
  • M. Negodaev,
  • W.-D. Nowak,
  • L. L. Pappalardo,
  • R. Perez-Benito,
  • N. Pickert,
  • P. E. Reimer,
  • A. R. Reolon,
  • C. Riedl,
  • K. Rith,
  • G. Rosner,
  • A. Rostomyan,
  • J. Rubin,
  • D. Ryckbosch,
  • Y. Salomatin,
  • F. Sanftl,
  • A. Schäfer,
  • G. Schnell,
  • K. P. Schüler,
  • B. Seitz,
  • T.-A. Shibata,
  • V. Shutov,
  • M. Stancari,
  • M. Statera,
  • E. Steffens,
  • J. J. M. Steijger,
  • F. Stinzing,
  • S. Taroian,
  • A. Terkulov,
  • A. Trzcinski,
  • M. Tytgat,
  • A. Vandenbroucke,
  • Y. Van Haarlem,
  • C. Van Hulse,
  • D. Veretennikov,
  • V. Vikhrov,
  • I. Vilardi,
  • S. Wang,
  • S. Yaschenko,
  • S. Yen,
  • W. Yu,
  • B. Zihlmann,
  • P. Zupranski

DOI
https://doi.org/10.1140/epjc/s10052-011-1609-2
Journal volume & issue
Vol. 71, no. 4
pp. 1 – 25

Abstract

Read online

Abstract Exclusive ρ 0-meson electroproduction is studied in the HERMES experiment, using a 27.6 GeV longitudinally polarized electron/positron beam and unpolarized hydrogen and deuterium targets in the kinematic region 0.5 GeV2<Q 2<7.0 GeV2, 3.0 GeV <W<6.3 GeV, and −t′<0.4 GeV2. Real and imaginary parts of the ratios of the natural-parity-exchange helicity amplitudes T 11 ( $\gamma^{*}_{T} \rightarrow\rho_{T}$ ), T 01 ( $\gamma^{*}_{T} \rightarrow \rho_{L}$ ), T 10 ( $\gamma^{*}_{L} \rightarrow\rho_{T}$ ), and T 1−1 ( $\gamma^{*}_{-T} \rightarrow\rho_{T}$ ) to T 00 ( $\gamma^{*}_{L}\rightarrow\rho_{L}$ ) are extracted from the data. For the unnatural-parity-exchange amplitude U 11, the ratio |U 11/T 00| is obtained. The Q 2 and t′ dependences of these ratios are presented and compared with perturbative QCD predictions.

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