ONE-LOOP INDUCED EFFECTIVE ON-SHELL Z-GAMMA-GAMMA-GAMMA INTERACTIONS

We give examples of lowest-dimensional effective Lagrangians describin g the decay Z --> yyy, induced at one-loop level within renormalizable models of electroweak interactions. The relevant coupling constants c orresponding to scalar, fermion and vector boson loops are specified. In general, the description in terms of a lowest-order effective Lagra ngian makes sense if the particles involved in the loops are heavy in comparison with the Z. However, such an approximation seems to work re markably well even for the W boson loops (though the m(w) is of the sa me order of magnitude as the m(z) owing to additional ''accidental'' c onvergence factors arising from integrals over Feynman parameters.