Charge symmetry violation in the parton distributions of the nucleon

We point out that charge symmetry violation in both the valence and sea quark distributions of the nucleon has a nonperturbative source. We calculate this nonperturbative charge symmetry violation using the meson cloud model which has earlier been successfully applied to the study of SU(2) flavor asymmetry in the nucleon sea and quark-antiquark asymmetry in the nucleon. By taking into account the mass differences among hadron multiplets and assuming the coupling constants respect isospin, we find that the charge symmetry violation in the minority quark distribution is well below $1\%,$ which is consistent with most low energy tests but significantly smaller than most quark model predictions of about 2–10 %. Our prediction for the charge symmetry violation in the sea quark distribution is also much smaller than the quark model calculation.