Phase-Parameter Representation of Neutron-Proton Scattering from 13.7 to 350 Mev

Abstract

Results of gradient searches, by means of an IBM 704 machine, for phase parameters representing neutron-proton scattering are reported. The analysis made use of most available measurements. The number of "measurements" used in the final searches was 293 with 35 additional ones which were used to obtain composite values. Most of the fits join reasonably smoothly to the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ phase shift curve at low energies. The validity of charge independence was assumed and the more probable among the T = 1 phase-parameter sets obtained in a previously described series of searches for phase-parameter fits to $p-p$ data were therefore employed for this T. The one-pion exchange values were used for the larger $L$ and $J$. Independent sets of searches started with phase parameters corresponding to the Gammel-Christian-Thaler potential, and the Gammel-Thaler potential, respectively. The procedure was varied by employing a weighted mean of fits obtained from the two different starting points as a new starting set and other devices described in the text. The final fits are appreciably better than the starts, the mean square deviation being reduced by a factor ∼20 in some cases. A rough division of the final fits into related families according to the behavior of the parameters $K_3$ and ${\rho }_3$ can be made. The value of additional measurements and especially those of the triple-scattering parameters and polarization correlation is pointed out. Tests on reasonableness of one of the better fits from the point of view of representation by a static potential have been made, with satisfactory results.