Proton-Neutron Mass Difference

Abstract

An expression for the electromagnetic self-mass of a physical nucleon is obtained from the basic postulates of field theory. A complete set of intermediate states is then introduced and the one-nucleon state and the state with one nucleon plus a nucleon pair are taken into account. Direct comparison is thus established between the various methods of obtaining the proton-neutron mass difference. The mass difference is computed by two methods which use the Stanford form factors. It is shown that if the form factor which agrees in the experimental region is used in the nonexperimental region in the nucleon-pair term, then there is a disagreement with the present electromagnetic explanation of the proton-neutron mass difference.