ISOSPIN-VIOLATING MESON-NUCLEON VERTICES AS AN ALTERNATE MECHANISM OFCHARGE-SYMMETRY BREAKING

We compute isospin-violating meson-nucleon coupling constants and thei r consequent charge-symmetry-breaking (CSB) nucleon-nucleon potentials . The couplings result from evaluating matrix elements of quark curren ts between nucleon states in a nonrelativistic constituent quark model ; the isospin violations arise from the difference in the up and down constituent quark masses. We find, in particular, that isospin violati on in the omega meson-nucleon vertex dominates the class TV CSB potent ial obtained from these considerations. We evaluate the resulting spin -singlet-triplet mixing angles, the quantities germane to the differen ce of neutron and proton analyzing powers measured in elastic (n) over right arrow-(p) over right arrow scattering, and find them commensura te to those computed originally using the on-shell value of the rho-om ega mixing amplitude. The use of the on-shell rho-omega mixing amplitu de at q(2)=0 has been called into question; rather, the amplitude is z ero in a wide class of models. Our model possesses no contribution fro m rho-omega mixing at q(2)=0, and find that omega-meson exchange suffi ces to explain the measured n-p analyzing power difference at 183 MeV.