Cross section and induced polarization in3Heelastic scattering at 443 MeV

Abstract

Angular distributions of the differential cross section and the induced polarization of ${}^{3}\mathrm{He}$ elastic scattering on ${}^{12}\mathrm{C},$ ${}^{58}\mathrm{Ni},$ and ${}^{90}\mathrm{Zr}$ targets were measured at 443 MeV incident energy. This is the first measurement of ${}^{3}\mathrm{He}$ spin observables at intermediate energies. Cross sections and polarizations were measured in the range of center-of-mass angles of $5\ifmmode^\circ\else\textdegree\fi{}--30\ifmmode^\circ\else\textdegree\fi{}$ and $5\ifmmode^\circ\else\textdegree\fi{}--20\ifmmode^\circ\else\textdegree\fi{},$ respectively. The polarization was measured with the focal plane polarimeter system of the Grand Raiden spectrometer, which was calibrated for ${}^{3}\mathrm{He}$ at the present energy. The optical potential parameters including the spin-orbit term were determined by a systematic search procedure. The diffuseness parameter of the spin-orbit potential was about 0.6--0.8 fm in contrast to much smaller values of 0.2--0.3 fm reported at lower energies. The energy dependence of the reduced volume integrals of the optical potential was found to be similar to that observed for protons at intermediate energies, but the real potential terms were smaller. Single folding (SF) model calculations were performed and compared with the experimental data. We found that the renormalization factors used to modify the SF potential were necessary in order to obtain a good fit to the data. These results call for an appropriate density dependent nucleon-nucleus interaction in the ${}^{3}\mathrm{He}$ nucleus.