Theoretical research on S-wave meson-2 nucleon 3 body systems

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The purpose of this research is to make clear the mechanisms for the scatterings and the reactions of the piNN and etaNN systems on a unified way based on the Faddeev formalism and to find characteristic phenomena such as dibaryons in these systems. Especially the phenomena which concern the S wave mesons are important subject.The piN interaction for input is represented in a separable form by use of phase-shift analysis results. On the other hand the NN interction is represented also in a separable form in an offshell equivalent way with Ueda-Green OBEP.Furthermore the piN-pN coupling, piDELTA*N vertex and the offshell freedom of the piN P_<33> interaction are taken into account. Faddeev equation is solved with these elements input. The processes of pp-pp, np-np, pp-pid, pid-pid, and pp-pnpi^+ are described in a unified way in quantitative consistence with experiment. A structure due tothe S wave pion is found near pion threshold in I=1, J^P=0^- channel.The Pauli principle forbids the NN state of I=0, J^P=0^- channel. Therefore, if a resonance exists in the piNN system in this channel, its decay width may be narrow. Near pion threshold we calculated the amplitude for piNN*piNN process in this channel. A resonance with such a narrow width as 30 MeV is found. This state is generated by S wave pion. On the other hand in piNN-etaNN system quasi bound state is generated due to S wave eta-meson near its threshold in I=0, J^P=1^- channel.