Differential cross section for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi><mml:mo>−</mml:mo><mml:mi>p</mml:mi></mml:math>elastic scattering in the angular range<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>51</mml:mn><mml:mi>°</mml:mi><mml:mo>&lt;</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>θ</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mo>&lt;</mml:mo><mml:mn>180</mml:mn><mml:mn/><mml:mi>°</mml:mi></mml:math>at 647.5 MeV

The $n\ensuremath{-}p$ elastic differential cross section in the angular range $51\ifmmode^\circ\else\textdegree\fi{}&lt;{\ensuremath{\theta}}^{*}&lt;180\ifmmode^\circ\else\textdegree\fi{}$ at 647.5 MeV has been measured with high statistical precision, good relative accuracy, and absolute normalization of 7% estimated accuracy (based on the observed yield of deuterons from $\mathrm{np}\ensuremath{\rightarrow}d{\ensuremath{\pi}}^{0}$). A monoenergetic neutron beam bombarded a liquid hydrogen target, and the protons and deuterons ejected from the target were detected by a multiwire proportional chamber spectrometer which measured their momentum, angle, and mass. The results resolve discrepancies between previous measurements of this observable, and are in reasonable agreement with Saclay data at large angles, and with a phase shift fit. Evidence for accuracy of the shape of the angular distribution is provided by the good value obtained for the pion-nucleon coupling constant (${f}^{2}=0.0759\ifmmode\pm\else\textpm\fi{}0.0030$) when the pole-extrapolation method of Chew is used to extract ${f}^{2}$ from this shape.NUCLEAR REACTIONS $^{1}\mathrm{H}(n, p)n$, ${T}_{n}=674.5$ MeV; measured $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}^{*}}$ vs ${\ensuremath{\theta}}^{*}$ for $51\ifmmode^\circ\else\textdegree\fi{}&lt;{\ensuremath{\theta}}^{*}&lt;180\ifmmode^\circ\else\textdegree\fi{}$.