Search for the deeply bound state from the semi-inclusive forward-neutron spectrum in the in-flight reaction on helium-3

Hashimoto, Tadashi*   ; Tanida, Kiyoshi   ; J-PARC E15 Collaboration*; 65 of others*

An experiment to search for the bound state was performed via the in-flight reaction using kaons at 1 GeV/ at the J-PARC hadron experimental facility. In the semi-inclusive neutron missing-mass spectrum at , no significant peak was observed in the region corresponding to binding energy larger than 80 MeV, where a bump structure has been reported in the final state in different reactions. Assuming the state to be isotropically decaying into , mass-dependent upper limits on the production cross section were determined to be 30-180, 70-250, and 100-270 b/sr, for the natural widths of 20, 60, and 100 MeV, respectively, at 95% confidence level.