ϵ b constraints on self-couplings of vector bosons

We analyze the constraints on possible anomalous contributions to the W⁺W^-Z vertex coming from non-universal radiative corrections to the Z → bb width. We parametrize these corrections in terms of ε{lunate}_b and use the LEP data to establish the allowed values for the anomalous triple couplings. We examine all CP conserving effective operators that exhibit SU(2)_L × U(1)_Y gauge invariance and do not give any tree level contribution to the present experimental observables. For some of these operators our constraints are comparable with the bounds coming from a global fit of the oblique parameters, which evidences the increasing relevance of the precise measurement of the b-quark parameters at LEP for the search of new physics.