Study of Nuclear Isovector Spin Response Functions by Quasi-elastic Scattering

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We developed a theoretical framework to analyse the spin observables of the charge exchange quasi-elastic scattering, which gives us information of the isovector spin response functions. The framework consists of three aspects: (1) Nuclear response functions are calculated by the continuum random phase approximation, which takes into account the radial dependent effective mass and the spreading widths of the particles and the holes, and include the Δ isobar; (2) One-step process of the reaction is calculated by the distorted wave impulse approximation; and (3) the two-step processes are estimated by the plane wave approximation. In the calculition of the one- and two-step processes, the above mentiond response functions are used.Using this theoretical framework we analysed ^<12>C, ^<40>Ca(p^^→, n^^→) reactions at 350 and 500MeV at various angles. The spin-longitudinal response functions were well reproduced, and consistent with long predicted enhancement. This is the first evidence of a precusor phenomenon of the pion condensation. We evaluated the Landau-Migdal parameters to reproduce the data. We found that the often used universality ansatz does not hold, and the obtained values are consitent with those obtaied from the Gamov-Teller transition strength distribution. Reproduction of the transverse response functions was much improved but not yet satisfactory.