Search for strange tribaryon states in the inclusive 4He(Kstopped−,p) reaction

A search for tribaryon states was performed at KEK-PS. We adopted the 4He(Kstopped−,p) reaction to populate the states with strangeness −1, charge 0 and isospin 1. No significant narrow structure was observed in the mass region from 3000 to 3200 MeV/c2 in an inclusive missing mass spectrum. The upper limit of the formation branching ratio was determined to be (0.4-6)×10−4, (0.2-6)×10−3 and (0.06-5)×10−2/(stoppedK−) with 95% confidence level for a narrow state with an assumed width of 0, 20 and 40 MeV/c2, respectively.