MASSES, MIXINGS, YUKAWA COUPLINGS AND THEIR SYMMETRIES

We present a method to find the number of real and imaginary observabl e parameters coming from the Yukawa sector in an arbitrary gauge theor y. The method leads naturally to a classification of Yukawa couplings according to their symmetries and suggests a new parametrization of ma sses and mixings that is useful to study the behaviour of Yukawa coupl ings under the renormalization group. We apply it to some examples bas ed on the Standard Model with Yukawa couplings obeying various chiral symmetries. We also show how our method of parameter counting can be u sed in some models with an enlarged leptonic sector.