The ηd Interaction Studied in γd→π⁰ηd

We have studied the interaction between the eta meson and deuteron (ξd interaction) from measurement of cross-sections for coherent neutral-pion and eta-meson photoproduction on the deuteron (γ d → π0 ξ d) using the photon beam at the Research Center for Electron Photon Science (ELPH), Tohoku University, Japan. We have found a narrow resonance-like peak in the ξd subsystem in the vicinity of the threshold, suggesting strong ξd attraction. The sharp backward-peaking angular dependence of deuteron emission, predicted by the existing theoretical calculations, does not appear. We discuss a possible production mechanism of the γ d → π0 ξ d reaction and the possibility of using coherent π0 and ξ photoproduction on a nucleus to study the ξ-nuclear interaction.