Measurement of then-pelastic scattering angular distribution atEn=10 MeV

Abstract

The relative differential cross section for the elastic scattering of neutrons by protons was measured at an incident neutron energy ${E}_{n}=14.9$ MeV and for center-of-mass scattering angles ranging from about ${60}^{\ifmmode^\circ\else\textdegree\fi{}}$ to ${180}^{\ifmmode^\circ\else\textdegree\fi{}}$. Angular distribution values were obtained from the normalization of the integrated data to the $n$-$p$ total elastic scattering cross section. Comparisons of the normalized data to the predictions of the Arndt et al. phase-shift analysis, those of the Nijmegen group, and with the ENDF/B-VII.0 evaluation are sensitive to the value of the total elastic scattering cross section used to normalize the data. The results of a fit to a first-order Legendre polynomial expansion are in good agreement in the backward scattering hemisphere with the predictions of the Arndt et al. phase-shift analysis, those of the Nijmegen group, and to a lesser extent, with the ENDF/B-VII.0 evaluation. A fit to a second-order expansion is in better agreement with the ENDF/B-VII.0 evaluation than with the other predictions, in particular when the total elastic scattering cross section given by Arndt et al. and the Nijmegen group is used to normalize the data. A Legendre polynomial fit to the existing $n$-$p$ scattering data in the 14 MeV energy region, excluding the present measurement, showed that a best fit is obtained for a second-order expansion. Furthermore, the Kolmogorov-Smirnov test confirms the general agreement in the backward scattering hemisphere and shows that significant differences between the database and the predictions occur in the angular range between ${60}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${120}^{\ifmmode^\circ\else\textdegree\fi{}}$ and below ${20}^{\ifmmode^\circ\else\textdegree\fi{}}$. Although there is good overall agreement in the backward scattering hemisphere, more precision small-angle scattering data and a better definition of the total elastic cross section are needed for an accurate determination of the shape and magnitude of the angular distribution.