New data on \(\vec{\gamma} \vec{p}\rightarrow \eta p\) with polarized photons and protons and their implications for \(N^ \to N\eta\) decays

• Published in: arXiv.org 2019-09
• Main Authors: Müller, J, Hartmann, J, Grüner, M, Afzal, F, Anisovich, A V, Bantes, B, Bayadilov, D, Beck, R, Becker, M, Beloglazov, Y, Berlin, M, Bichow, M, Böse, S, K -T Brinkmann, Challand, T, Crede, V, Dietz, F, Dieterle, M, Drexler, P, Dutz, H, Eberhardt, H, Elsner, D, Ewald, R, net-Ponse, K, Friedrich, S, Frommberger, F, Funke, C, Gottschall, M, Gridnev, A, Goertz, S, Gutz, E, Hammann, C, Hannen, V, Hannappel, J, Herick, J, Hillert, W, Hoffmeister, P, Honisch, C, Jahn, O, Jude, T, Jaegle, I, Käser, A, Kaiser, D, Kalinowsky, H, Kalischewski, F, Kammer, S, Keshelashvili, I, Klassen, P, Kleber, V, Klein, F, Klempt, E, Koop, K, Krusche, B, Kube, M, Lang, M, Lopatin, I, Maghrbi, Y, Mahlberg, P, Makonyi, K, Messi, F, Metag, V, Meyer, W, Müllers, J, Nanova, M, Nikonov, V, Novinski, D, Novotny, R, Piontek, D, Reicherz, G, Rosenbaum, C, Rostomyan, T, Roth, B, Sarantsev, A, Schmidt, C, Schmieden, H, Schmitz, R, Seifen, T, Sokhoyan, V, Thiel, A, Thoma, U, Urban, M, H van Pee, Walther, D, Wendel, C, Wiedner, U, Wilson, A, Winnebeck, A, Witthauer, L, CBELSA/TAPS Collaboration
• Format: Article
• Language: English
• Subjects: Eta-mesons; Nucleons; Photons; Photoproduction; Protons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1909.08464

The polarization observables \(T, E, P, H\), and \(G\) in photoproduction of \(\eta\) mesons off protons are measured for photon energies from threshold to \(W=2400\,\)MeV (\(T\)), 2280 MeV (\(E\)), 1620 MeV (\(P, H\)), or 1820 MeV (\(G\)), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, J\"uBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the \(N\eta\) decay of nucleon resonances. A \(N\eta\)-branching ratio of \(0.33\pm 0.04\) for \(N(1650)1/2^-\) is found, which reduces the large and controversially discussed \(N\eta\)-branching ratio difference of the two lowest mass \(J^P=1/2^-\)-resonances significantly.