Kaonic nuclear state search via K− reaction at rest on 4He target

Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon S0(3115) obtained in KEK PS-E471. In contrast to the previous proton spectrum, no narrow (∼20 MeV) peak structure was found either in the inclusive 4He(stopped K−, p) or in the semi-inclusive 4He(stopped K−, pX±) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to S0(3115), has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure.