Meson-loop contributions to the rho-omega mass splitting and rho charge radius - art. no. 054030

Contributions of two-pseudoscalar and vector-pseudoscalar meson loops to th e rho-omega mass splitting are evaluated in a covariant model based on stud ies of the Schwinger-Dyson equations of QCD. The role and importance of the different time orderings of the meson leaps are analyzed and compared with those obtained within time-ordered perturbation theory. It is shown that e ach meson loop contributes less than 10% of the bare mass, and decreases as the masses of the intermediate mesons increase beyond approximately m(rho) /2. A mass splitting of m(omega)-m(rho)approximate to 25 MeV is obtained fr om the pi pi, K (K) over bar, omega pi, rho pi, omega eta, rho eta and K*K channels. The model is then used to determine the effect of the two-pion lo op on the rho-meson electromagnetic form factor. It is shown that the inclu sion of pion loops increases the rho-meson charge radius by 10%. [S0556-282 1(99)01617-3].