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The $eta$ mesic nucleus is considered to be one of the interesting exotic many body systems and has been studied since 1980s theoretically and experimentally. Recently, the formation of the $eta$ mesic nucleus in the fusion reactions of the light nuclei such as $d + d rightarrow (eta + alpha) rightarrow X$ has been proposed and the experiments have been performed by WASA-at-COSY. We develop a theoretical model to evaluate the formation rate of the $eta$ mesic nucleus in the fusion reactions and show the calculated results. We find that the $eta$ bound states could be observed in the reactions in cases with the strong attractive and small absorptive $eta$-nucleus interactions. We compare our results with existing data of the $d + d rightarrow eta + alpha$ and the $d + d rightarrow {^3 rm He} + N + pi$ reactions. We find that the analyses by our theoretical model with the existing data can provide new information on the $eta$-nucleus interaction.
We consider the reaction g+d -> pi+d in a wide energy range around and above the eta-meson photoproduction threshold at backward CM angles of the outgoing pion. Our theoretical analysis is essentially motivated by the recent measurements of the CLAS
The total cross section of the p d -> p d eta reaction has been measured at two energies near threshold by detecting the final proton and deuteron in a magneti spectrometer. The values are somewhat larger than expected on the basis of two simple theoretical estimates.
We theoretically investigate a possibility of an $eta ^{prime} d$ bound state and its formation in the $gamma d to eta d$ reaction. First, in the fixed center approximation to the Faddeev equations we obtain an $eta ^{prime} d$ bound state with a bin
A model for the p d --> p d eta reaction published earlier, including the final state interaction (FSI) of all particles, is revisited to investigate the low energy data on this reaction. The three body problem of p-d-eta scattering in the final stat
We study $eta$ photoproduction off the deuteron ($gamma dtoeta pn$) at a special kinematics: $sim 0.94$ GeV of the photon beam energy and $sim 0^circ$ of the scattering angle of the proton. This kinematics is ideal to extract the low-energy $eta$-nuc