MECHANISM FOR OBTAINING A NEGATIVE-T OBLIQUE PARAMETER

It is pointed out that a simple way for obtaining T < 0 is to mix states with different third components of the weak isospin, yielding a current coupling to W3 which is not flavor diagonal. We illustrate this mechanism in two known cases where one may have T < 0, and then use it to obtain another case where, with either fermions or scalars, a negative T occurs. We can also obtain a sizable negative contribution for the oblique parameter S by using its dependence on the hypercharge, and thus satisfy all the present experimental constraints on both parameters.