Measurement of the Backward-to-90-degrees Neutron-proton Elastic Cross-section Ratio Between 40 and 75 Mev

The ratio of the 166\ifmmode^\circ\else\textdegree\fi{} c.m. to 90\ifmmode^\circ\else\textdegree\fi{} c.m. and of the 178.5\ifmmode^\circ\else\textdegree\fi{} c.m. to 90\ifmmode^\circ\else\textdegree\fi{} c.m. differential cross section for neutron-proton scattering has been measured between 40 and 75 MeV. The trend of our data is slightly higher than the present phase-shift analysis.