Comment on theS01Nucleon-Nucleon Effective-Range Expansion Parameters

Abstract

The most accurate nucleon-nucleon scattering experiments below 10 MeV are now consistent with the following values and uncertainties for the $^{1}S_{0}$ scattering lengths and effective ranges: ${a}_{\mathrm{pp}}^{c}=\ensuremath{-}7.823\ifmmode\pm\else\textpm\fi{}0.01F$ ${r}_{\mathrm{pp}}^{c}=2.794\ifmmode\pm\else\textpm\fi{}0.015F$ ${a}_{\mathrm{nn}}=\ensuremath{-}17\ifmmode\pm\else\textpm\fi{}1F$ ${r}_{\mathrm{nn}}=2.84\ifmmode\pm\else\textpm\fi{}0.03F$ ${a}_{\mathrm{np}}=\ensuremath{-}23.715\ifmmode\pm\else\textpm\fi{}0.015F$ ${r}_{\mathrm{np}}=2.73\ifmmode\pm\else\textpm\fi{}0.03F$ Unless strong theoretical arguments can be advanced that all charge-dependent corrections to the parameters can be calculated accurately enough to prove that the values ${a}_{\mathrm{nn}}$, ${r}_{\mathrm{nn}}$, or ${r}_{\mathrm{np}}$ must be moved outside these limits, or strong experimental reasons given to believe that experiments leading to these results were significantly in error, it is argued that new calculations or experiments aimed at changing these values are likely to fail. This argument is supported by an analysis of the latest $p\ensuremath{-}p$ experiments of Jarmie, Jett, Detch, and Hutson at 9.918 MeV, which reconfirm the one-pion-exchange shape effect and give ${G}_{{\ensuremath{\pi}}^{0}p}^{2}=15.3\ifmmode\pm\else\textpm\fi{}2.4$ for the pion-nucleon coupling constant.