Charge-symmetry breaking in neutron-proton scattering: Isospin-mixing parameter

Abstract

An isospin-mixing parameter due to charge-symmetry breaking in the neutron-proton system is calculated in a new way, using the distorted-wave Born approximation. Three mechanisms of charge-symmetry breaking are investigated: one-photon exchange, rho-omega mixing, and the nucleon mass-difference effect in one-pion exchange. Numerical calculation of this parameter for a number of energies and angular momenta yields some interesting systematic behavior. In particular, for center-of-mass energies 100 MeV and greater, the largest values are obtained for total angular momentum J=2 (or 4). The mass-difference effect is the most dominant one for all energies greater than 100 MeV. The analyzing-power difference, which is measurable experimentally, is also calculated.