[ ~ Nuclear Physics B16 (1970) 503-507. North-Holland Publ. Comp., Amsterdam OBSERVATION OF A A++( -~ 1900) RESONANCE DECAYING INTO A++(1236)Tr-Tr+ H.BOGGILD, K.HANSEN, H.JOHNSTAD, R.MOLLERUD and L.VEJE The Niels Bohr Institute, University of Copenhagen M.K.KORKEA-AHO, P.LAURIKAINEN and R.O.RAITIO Department of Nuelear Physies, University of Helsinki T.JACOBSEN and S.O.SORENSEN Institute of Physics, University of Oslo G.EKSPONG, L.GRANSTROM, S.O.HOLMGREN, S.NILSSON, U.SVEDIN and N,YAMDAGNI Institute of Physics, University of Stockholm Received 15 September 1969 Abstract: Production of A++( ~ 1900) has been observed in the reaction pp ~ A++(~ 1900)n. The observed decay mode is A++(~ 1900) -+ A++(1236)Tr-Tr +. The cross section for the process multiplied by the branching ratio of the observed decay mode is 29 + 7 /~b. There is no indication of the decay mode A++(~I900) ~ A++(1236) pO(765). Studies of multiparticle final states i~J high-energy proton-proton and pion- proton interactions indicate the presence of higher nucleon resonances decaying into the A++(1236) with one or more pions. In a study of proton-proton inter- actions at 19 GeV/c we find evidence for the production of a A ++ resonance at about 1.9 GeV/c 2 and its decay mode A++(~ 1900) ~ A++(1236)Tr-~r + . (1) The analysis is based on approximately 30 000 four-prong events processed with the CERN THRESH-GRIND programs. Fits were obtained to the three channels pp ~ ppTr+Tr - , (2) pp ~ pprr÷n-~r ° , (3) pp ~ npn + 7r + lr- . (4)