Nucleon-nucleon scattering analyses. II. Neutron-proton scattering from 0 to 425 MeV and proton-proton scattering from 1 to 500 MeV

Abstract

The first paper of this series reported on energy-dependent and energy-independent phase-shift analyses of proton-proton elastic scattering data between 1 and 500 MeV. The present paper extends the analysis to include neutron-proton elastic scattering data between 0 and 425 MeV. Although this analysis is similar to those of the Livermore series, it differs in a number of important respects. First, a charge-splitting prescription has been employed for the isovector phases which includes Coulomb barrier effects and takes into account the difference in the masses between charged and uncharged pions. Second, a $K$-matrix formalism has been used to impose the constraints of the deuteron pole and the peripheral interaction (one-pion-exchange contribution) on the energy-dependent representation. Third, the neutron-proton and proton-proton scattering data have been fitted simultaneously in the search. The energy-dependent solution obtained uses 46 phenomenological parameters to represent 2670 data, with ${\ensuremath{\chi}}^{2}=2815$. A number of the neutron-proton phases have changed from the values obtained in Livermore $X$ at higher energies, but the low-energy behavior is largely unaltered. A notable exception is the mixing parameter ${\ensuremath{\epsilon}}_{1}$ which has been strongly affected by the deuteron pole. The proton-proton phases are changed very slightly from the paper I values as a result of the additional $n\ensuremath{-}p$ constraints upon the $I=1$ phases. We feel that the net result of these alterations is a more compact and reliable representation of nucleon-nucleon scattering in the energy range considered.NUCLEAR STRUCTURE Energy-dependent and energy-independent phase-shift combined analyses of 1-425 MeV $n\ensuremath{-}p$ and 1-500 MeV $p\ensuremath{-}p$ scattering data.