Production of $a_0$-mesons in the reactions $\pi N \to a_0 N$ and $p p   \to d a_0^+$ at GeV energies
  We investigate the reactions $\pi N \to a_0 N$ and $p p \to d a_0^+$ near threshold and at medium energies. An effective Lagragian approach and the Regge pole model are applied to analyze different contributions to the cross section of the reaction $\pi N \to a_0 N$. These results are used to calculate the differential and total cross sections of the reaction $p p \to d a_0^+$ within the framework of the two-step model in which two nucleons produce an $a_0$-meson via $\pi$ -meson exchange and fuse to a deuteron. The necessity of new measurements on $a_0$ production and branching fractions (of its decay to the $K\bar K$ and $\pi\eta$ channels) is emphasized for clarifying the $a_0$ structure. Detailed predictions for the reaction $pp \to d a_0^+$ are presented for the energy regime of the proton synchrotron COSY-J\"ulich. 
V. Yu. Grishina (INR, Moscow), L. A. Kondratyuk (ITEP, Moscow), E. L.   Bratkovskaya (Univ. Giessen), M. Buescher (FZ Juelic...