Photoproduction of $\hat{I}\cdot$ and $\hat{I}{\cdot }^{\prime }$ Mesons on Proton

Abstract

New high-precision total and differential cross sections for $\hat{I}\cdot$ and $\hat{I}{\cdot }^{\prime }$ photoproduction on the proton obtained by the A2 Collaboration at the Mainz Microtron are presented. The data for $\hat{I}\cdot$ photoproduction demonstrate a cusp at the energy W$\sim$1.9~GeV. Furthermore, we present a new version of the $\hat{I}\cdot$MAID model for $\hat{I}\cdot$ and $\hat{I}{\cdot }^{\prime }$ photoproduction. The model includes 23 nucleon resonances parametrized with Breit-Wigner shapes. The background is described by vector and axial-vector meson exchanges in the $t$ channel using the Regge phenomenology. Parameters of the resonances were obtained from a fit to preliminary data of the A2 Collaboration at MAMI and available data from other collaborations. The cusp is explained as a threshold effect due to the opening $\hat{I}{\cdot }^{\prime }p$ decay channel of the $N(1895)1/2^{-}$ resonance.

5 pages, 5 figures, 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto, Japan