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

floyd a. beams, joseph h. anthony, bruce bettinghaus, kenneth smith;

An experiment to search for the K− pp bound state was performed via the in-flight 3He(K−, n) reaction using 5.3 × 109 kaons at 1GeV/c at the J-PARC hadron experimental facility. In the semi-inclusive neutron missing-mass spectrum at θlab n = 0◦, no significant peak was observed in the region corresponding to K− pp binding energy larger than 80MeV, where a bump structure has been reported in the p final state in different reactions. Assuming the state to be isotropically decaying into p, mass-dependent upper limits on the production cross section were determined to be 30–180, 70–250, and 100–270μb/sr, for the natural widths of 20, 60, and 100MeV, respectively, at 95% confidence level.