Neutron-Proton Forward-Angle Elastic Cross Sections at 790 MeV

Abstract

High-statistics measurements of the absolute differential cross section for $n\ensuremath{-}p$ scattering have been made over neutron c.m.-system scattering angles $9.5\ifmmode^\circ\else\textdegree\fi{}<{\ensuremath{\theta}}^{*}<64.5\ifmmode^\circ\else\textdegree\fi{}$. The statistical error is 1.7 to 3.3% for 2\ifmmode^\circ\else\textdegree\fi{}-wide angular bins, and the systematic error is 2.7 to 3.3%. The cross section is fitted by $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}^{*}}=A \mathrm{exp}(\mathrm{bt})$, with $A=10.27\ifmmode\pm\else\textpm\fi{}0.36$ mb/sr, $b=5.00\ifmmode\pm\else\textpm\fi{}0.05$, and $0.01<\ensuremath{-}t<0.39$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. For the ratio of the real to the imaginary part of the forward-scattering amplitude we obtained ${\ensuremath{\alpha}}_{n}>~\ensuremath{-}0.43\ifmmode\pm\else\textpm\fi{}0.04$, consistent with other less precise determinations of ${\ensuremath{\alpha}}_{n}$.