Implications of nucleon-nucleon spin-polarization measurements

Abstract

We discuss available data for spin observables in $\mathrm{pp}$ and $\mathrm{np}$ elastic scattering above 3 GeV/c. We identify those measurements which isolate exchange-amplitude components of specific interest---those which provide firm tests of Regge-exchange models and, on the other hand, those which models are unable to predict reliably. Using a simple Regge-pole-exchange model whose trajectory parameters and coupling properties are determined from data on other reactions, we compute expectations for all available $\mathrm{pp}$ spin observables and find good agreement with the data. We find that a hadronic axial-vector ${A}_{1}$-like exchange term is present in the data with strength compatible with theoretical estimates. The low-lying isoscalar exchange observed in $\mathrm{pp}$ and $\mathrm{np}$ polarization is consistent with estimates based on $\ensuremath{\epsilon}({0}^{++})$ exchange. We make a careful study of possible nonasymptotic Regge contributions which could obscure the interpretation of amplitude structure at momenta up to 6 GeV/c. We provide predictions for spin-correlation observables in $\mathrm{np}$ elastic and in $\mathrm{np}$ charge-exchange scattering.