Charge symmetry breaking and parity violating electron-proton scattering

Abstract

Charge symmetry breaking contributions to the proton's neutral weak form factors must be understood in order for future measurements of parity violating electron-proton scattering to be definitively interpreted as evidence of proton strangeness. We calculate these charge symmetry breaking form factor contributions using chiral perturbation theory with resonance saturation estimates for unknown low-energy constants. The uncertainty of the leading-order resonance prediction is reduced by incorporating nuclear physics constraints. Higher-order contributions are investigated through phenomenological vertex form factors. We predict that charge symmetry breaking form factor contributions are an order of magnitude larger than expected from na\"{\i}ve dimensional analysis but are still an order of magnitude smaller than current experimental bounds on proton strangeness. This is consistent with previous calculations using chiral perturbation theory with resonance saturation.