Trilinear neutral gauge boson couplings in effective theories - art. no. 113014

We list all the lowest dimension effective operators inducing off-shell tri linear neutral gauge boson couplings ZZ gamma, Z gamma gamma, and ZZZ withi n the effective Lagrangian approach, both in the linear and nonlinear reali zations of SU(2)(L) x U(1)(Y) gauge symmetry. In the linear scenario we fin d that these couplings can be generated only by dimension-8 operators neces sarily including the Higgs boson field, whereas in the nonlinear case they are induced by dimension-6 operators. We consider the impact of these coupl ings on some precision measurements such as the magnetic and electric dipol e moments of fermions, as well as the Z boson rare decay Z --> nu<(<nu>)ove r bar>gamma. If the underlying new physics is of a decoupling nature, it is not expected that trilinear neutral gauge boson couplings may affect consi derably any of these observables. Oh the contrary, it is just in the nonlin ear scenario where these couplings have the more promising prospects of bei ng perceptible through high precision experiments.