Spin correlation coefficient for proton-He-3 elastic scattering at 100 MeV

We present the measured spin correlation coefficient C-y,C-y for p- He-3 elastic scattering at 100 MeV at the angles theta(c.m.) = 46.9 degrees-149.2 degrees in the center-of-mass system. The Cy,y data and the existing cross section data are compared with rigorous four-nucleon scattering calculations based on realistic nucleon-nucleon potentials. Large differences are seen in the regime around the cross section minimum for both observables. The Delta isobar effects estimated by the NN + N Delta coupled-channels approach are small for the cross section. Meanwhile, in C-y,C-y, the Delta-isobar effects improve the agreement with the data. The analysis of the p- 3He elastic scattering amplitudes implies the necessity of three-nucleon forces (3NFs) that enhance the vector components in the amplitudes. The obtained results indicate that the spin correlation coefficient C-y,C-y expands the knowledge of the nuclear interactions with the Delta isobar or those including 3NFs that are masked in nucleon-deuteron elastic scattering.