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arXiv · 1408.3274

Measurement of the transverse target and beam-target asymmetries in $\eta$ meson photoproduction at MAMI

C. S. Akondi·J. R. M. Annand·H. J. Arends·R. Beck·A. Bernstein·N. Borisov·A. Braghieri·W. J. Briscoe·S. Cherepnya·C. Collicott·S. Costanza·E. J. Downie·M. Dieterle·A. Fix·L. V. Fil'kov·S. Garni·D. I. Glazier·W. Gradl·G. Gurevich·P. Hall Barrientos·D. Hamilton·D. Hornidge·D. Howdle·G. M. Huber·V. L. Kashevarov·I. Keshelashvili·R. Kondratiev·M. Korolija·B. Krusche·A. Lazarev·V. Lisin·K. Livingston·I. J. D. MacGregor·J. Mancel·D. M. Manley·P. Martel·E. F. McNicoll·W. Meyer·D. Middleton·R. Miskimen·A. Mushkarenkov·B. M. K. Nefkens·A. Neganov·A. Nikolaev·M. Oberle·M. Ostrick·H. Ortega·P. Ott·P. B. Otte·B. Oussena·P. Pedroni·A. Polonski·V. V. Polyanski·S. Prakhov·G. Reicherz·T. Rostomyan·A. Sarty·S. Schumann·O. Steffen·I. I. Strakovsky·Th. Strub·I. Supek·L. Tiator·A. Thomas·M. Unverzagt·Yu. A. Usov·D. P. Watts·D. Werthmüller·L. Witthauer·M. Wolfes
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Abstract

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of $\eta$ meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

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C. S. Akondi, J. R. M. Annand, H. J. Arends, R. Beck, A. Bernstein, N. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, C. Collicott, S. Costanza, E. J. Downie, M. Dieterle, A. Fix, L. V. Fil'kov, S. Garni, D. I. Glazier, W. Gradl, G. Gurevich, P. Hall Barrientos, D. Hamilton, D. Hornidge, D. Howdle, G. M. Huber, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, V. Lisin, K. Livingston, I. J. D. MacGregor, J. Mancel, D. M. Manley, P. Martel, E. F. McNicoll, W. Meyer, D. Middleton, R. Miskimen, A. Mushkarenkov, B. M. K. Nefkens, A. Neganov, A. Nikolaev, M. Oberle, M. Ostrick, H. Ortega, P. Ott, P. B. Otte, B. Oussena, P. Pedroni, A. Polonski, V. V. Polyanski, S. Prakhov, G. Reicherz, T. Rostomyan, A. Sarty, S. Schumann, O. Steffen, I. I. Strakovsky, Th. Strub, I. Supek, L. Tiator, A. Thomas, M. Unverzagt, Yu. A. Usov, D. P. Watts, D. Werthmüller, L. Witthauer, M. Wolfes. 2014-08-14. Measurement of the transverse target and beam-target asymmetries in $\eta$ meson photoproduction at MAMI. https://doi.org/10.1103/physrevlett.113.102001

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