Search for deeply bound kaonic state

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In order to observe deeply bound kaonic nuclear states, we carried out series of experiments (E471/E549/E570) at KEK-PS. If the interaction between kaon and nucleus is strongly attractive, K meson attracts neighboring nucleons and can form high density nuclear matter and can form deeply bound kaonic nuclei.When the binding becomes large, its major decay channel closes and the kaonic nuclei can have narrow widths. To this end, we measured neutron/proton spectra from ^4He(K-stopped, N) reactions. In both of neutron/proton spectra, we do not observe narrow peaks in the inclusive spectra. Tight upper limits for the formation rate of narrow kaonic states were obtained ftom both of neutron and proton spectra. We once reported a narrow peak -S0(3115)- in the proton spectrum in E471 experiment, it was found to be due to the experimental artifacts from the in results of the dedicated high-statistics experiment, E549.Thanks to the high statistics of E549/E570 data, we could successfully measure the energy and angular correlation of hyperon (Λ or Σ) and nucleon(s) (n/p or d). Especially, exclusive measurement of Λnd channel opened the door to investigate the gate to study the kaonic nuclear states with relatively broad widths. We are now planning to do exclusive measurement of K-pp system with ^3He(in-flight K-,n) reaction at J-PARC.