Nucleon - nucleon scattering near 50 MeV. III. Analysis of new Davisnpdifferential cross-section data

Abstract

New Davis $\mathrm{np}$ differential cross-section data at 50 MeV are phase-shift-analyzed together with the other world $\mathrm{pp}$ and $\mathrm{np}$ data in the laboratory scattering energy range 47.5 to 60.9 MeV. Various combinations of the $\mathrm{np}$ $\frac{d\sigma }{d\Omega }$ data, taken by groups at Davis, Oak Ridge, and Harwell, are included in the analysis and are found to affect mainly just the phase parameter $\delta \left({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\right)$. We argue that the Harwell only, or Harwell + Oak Ridge + Davis data analyses call for a strong long-range potential such as might come from ABC (Abashian-Booth-Crowe) exchange, while the Davis only or Davis + Oak Ridge data analyses are compatible with ordinary (non-ABC) meson-theoretical models. We urge that more precise $\mathrm{np}$ absolute $\frac{d\sigma }{d\Omega }$ data be taken, to 1 or 2% accuracy, especially at far forward angles.