Study of Nuclear Spin Excitations through All Polarization Transfer Measurements

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A main purpose of this research is to investigate spin excitations to unnatural parity states in nuclei by measuring all polarization transfer coefficients (D_<ij>'s) of proton scattering using a high resolution spectrograph and a focal plane polarimeter (FPP). The construction of the whole FPP system has been finished after newly introducing two MWPC's for measuring incident direction to its analyzer target of double scattering, which has been made by this Grant-in-Aid for Scientific Research. Moreover we have developed a high-speed dataacquisition system(-1Mbyte/sec)by excluding CAMAC actions from data flow.We have succeeded for the first time to measure D_<ij>'s in proton inelastic scattering off ^<12>C and ^<28>Si at zero degrees by fully utilizing above system. The results have shown that even the isoscalar spin-dependent term V_o, which is the smallest part of effective nucleon-nucleon (NN) interactions, can be 'determined with less ambiguities through the transitious to isoscalar 1^+ states. In addition, we have demonstrated that cross sections can be clearly disentangled with respect to the spin-flip and non spin-flip parts by a combination of all D_<ij'>. A selectivity of the isospin of the spin-flip transitions has also been found. As another theme, spin rotation parameters of proton elastic scattering have been measured by using this FPP system and medium modifications of NN interaction has been studied. Sonic new relevant experiments which investigate resonance modes of highly excited states and distributions of neutron densities are now under progress.