# Ratios of helicity amplitudes for exclusive $ρ^0$ electroproduction on transversely polarized protons

**Authors:**The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, S. Belostotski, H. P. Blok, A. Borissov, V. Bryzgalov, G. P. Capitani, G. Ciullo, M. Contalbrigo, W. Deconinck, R. De Leo, E. De Sanctis, M. Düren, G. Elbakian, F. Ellinghaus, L. Felawka, S. Frullani, F. Garibaldi, G. Gavrilov, V. Gharibyan, S. V. Goloskokov, Y. Holler, A. Ivanilov, H. E. Jackson, S. Joosten, R. Kaiser, G. Karyan, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, P. Kroll, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, W. Lorenzon, S. I. Manaenkov, B. Marianski, H. Marukyan, Y. Miyachi, A. Movsisyan, V. Muccifora, A. Nass, W. -D. Nowak, L. L. Pappalardo, A. Petrosyan, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, D. Ryckbosch, Y. Salomatin, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Statera, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Yaschenko, B. Zihlmann, P. Zupranski

Exclusive $\rho^0$-meson electroproduction is studied by the HERMES
experiment, using the 27.6 GeV longitudinally polarized electron/positron beam
of HERA and a transversely polarized hydrogen target, in the kinematic region
1.0 GeV$^2$

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