Charge-Symmetry-Breaking Potentials from Isospin-Violating Meson-Baryon Coupling Constants

Abstract

We consider charge-symmetry violations in the nucleon-nucleon force which result from isospin-violating meson-baryon coupling constants. The vector mesons are assumed to couple to the nucleon's electromagnetic current, which we decompose into isoscalar and isovector quark components. We compute these currents in the context of a constituent quark model. The isospin violations in the meson-baryon couplings arise from the difference in the up and down constituent quark masses. We show that class IV charge-symmetry-breaking potentials arise in the resulting $\omega$ and $\rho$ exchange contributions to the $NN$ force. The magnitude of these contributions is consistent with that phenomenologically required by the measured difference of $n$ and $p$ analyzing powers in elastic $\vec{n}-\vec{p}$ scattering at 183 MeV.