S-MATRIX ANALYSIS OF HEAVY-ION ELASTIC-SCATTERING

A procedure to minimize chi(2) is described which explores the fact th at the chi(2) distribution is of the fourth degree in the S-matrix ele ments. The fact that all three roots of the scale parameter for the mi nimum of chi(2) in its gradient direction are algebraically determined gives the present procedure some global features that previous method s did nor contemplate. The automatic search procedure also preserves t he unitary bound constraint of the S-matrix at every step. When the se arch in the gradient direction slows down, the procedure reverts to th e traditional quadratic approximation with zero-order regularization. The method is applied to the elastic scattering of the C-12 + O-16 rea ction near the Coulomb barrier.