Study of photo-neutron reaction below the pion threshold

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Main purpose of the profect was to elucidate the role of meson exchange current in photonuclear reactions. Tohoku and Melbourne resarchers have collaborated in photonuclear experiments using tagged photon faility of Tohoku University since 1982. The collaboration has found the importance of two nucleon absorption process in photonuclear reactions above the giant resonances but below the photo-pion threshold. Further detailed studies of the two-nucleon absorption mechanism have been pursued in the present short term project.In the first stage of the project, we have prepared experimental environment such as constructions of a new beam line, large volume neutron detectors and a new data acquisition system. All of these have been completed with success, and the performanses have been published.Collaborative experiments caried out in this term of the project are ^<16>O(gamma, n), ^<12>C(gamma, n) and ^<31>P(gamma, p). Also^<12>C(gamma, p) which was made before the project has been reanalyzed and published in Phys. Rev.C.One of the Melbourn collaborator, G.J.O'keefe, has completed his PhD thesis by the ^<16>O(gamma, n) result. The analysis of the ^<31>P(gamma, p) experiment has been finished. We have found a large population to the giant resonance region of the residual ^<30>Si nucleus, which shows a clear evidence of the interaction of photons with the meson exchange current. A part of the results has been presented at 1995 ICTP conference in Trieste/Itary.Altogether 6 researchers from Tohoku university have visited Melbourne university in 1994-1995. Altogether 9 researchers from Melbourne university have visited Tohoku university in 19941995.In January, 1996,3 researchers from Melbourne university have been invited to Tohoku university for discussions on the collaboration.In March, 1996,2 researchers from Melbourne university will be invited for the workshop on next collaborative experiments.