CoInvestigator(Kenkyūbuntansha) 
WAKAMATSU Masashi Graduate School of Science, Osaka University, associated professor, 大学院・理学研究科, 助教授 (40135653)
SATO Toru Graduate School of Science, Osaka University, associated professor, 大学院・理学研究科, 助教授 (10135650)

Budget Amount *help 
¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥700,000 (Direct Cost : ¥700,000)

Research Abstract 
1) The nuclear effective interactions above the mesonproduction : We constructed a new formalism which enables us to construct the effective interaction of baryons andmesons in nuclei which seems a natural extension of the traditional nuclear interactions. The idea is to remove any virtual interactions at all the real processes by the unitary transformation. As a result, we found that our onepoinexchange and static twopion exchange potentials coincide with the conventional potentials. At the same time, we obtained general baryonbaryon and mesonbaryon potentials, and the exchange electromagnetic currents. The exchange current which does not include isobar excitation is the same as the conventional one, and the current associated with isobar excitation is consistent with the baryonbaryon force. This formalism enables us to study the strong and electromagnetic phenomena in nuclei including the meson production and annihilation processes. The basic interaction for pionnucleon scatte
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ring and pion photoproduction was successfully studied. Also threshold neutral pion production by pp collision was studied. At present, study of the reactions (pi, eta), (gamma, eta) is in progress. 2) Pionnuclear reaction : As a first step toward the study of nuclear response by electromagentic interaction above mesonproduction threshold, we studied the properties of isobar spreading potential through the elastic and charge exchange pionnucleus scattering and the analysing power around the (3,3) resonance. For this purpose, we gave a formalism of isobardoorway state model which enables us to study the pion scattering by the open shell nuclei. By investigating pion scattering by ^<12>C,^<13>C,^<15>N and ^<16>O,we clarified existence of the Lane term as well as the spinorbit term which are energyindependent. The enphasis should be placed on that these two terms allow us to describe correctly the absolute magnitude of chargeexchange scattering and also signs of analysing power. At present, pionphotoproduction on the pshell nuclei around (3,3) resonance is under investigation based on the present model. 3) Baryon Structure in chiral soliton quark model : Structure of vertex functions in the effective hadorn interaction is essentially important in the nuclear phenomena at high momentum transfer. As a first step for thsi, we studied magnetic moments of baryons by adopting the SU (3) chiral soliton quark model inspired by the QCD theory. By including quarkmass difference between u (and/or d) and s as a symmetry breaking term, we obtained a good agreement between the theory and the experiment for the Octet baryons, and also results for the Decuplet baryons similar to the lattice calculation. These results imply large reliability of the model for the structure of vertex function. Also the Godfried sum was studied successfully. Less
