Quark-parton models and the neutron charge radius

Abstract
We point out that in parton models of nucleons, including standard constituent-quark models, the nonvanishing of the neutron charge radius implies an essential mixing of the space part of the nucleon wave function with those parts involving isospin and other discrete quantum numbers. We state these conditions precisely, and give a new value for this charge radius, derived from precise electron-deuteron scattering data.