Meson-loop contributions to the ρ-ω mass splitting and ρ charge radius

Contributions of two-pseudoscalar and vector-pseudoscalar meson loops to the {ρ}-{ω} mass splitting are evaluated in a covariant model based on studies of the Schwinger-Dyson equations of QCD. The role and importance of the different time orderings of the meson loops are analyzed and compared with those obtained within time-ordered perturbation theory. It is shown that each meson loop contributes less than 10% of the bare mass, and decreases as the masses of the intermediate mesons increase beyond approximately m_ρ/2. A mass splitting of m_ω-m_ρ≈25 MeV is obtained from the {π}{π}, KK̄, {ω}{π}, {ρ}{π}, {ω}{η}, {ρ}{η} and K*K channels. The model is then used to determine the effect of the two-pion loop on the {ρ}-meson electromagnetic form factor. It is shown that the inclusion of pion loops increases the {ρ}-meson charge radius by 10%.