hep-ph/9709297
Negative contributions to S in an effective field theory
Authors: Bogdan A. Dobrescu, John Terning
Journal-ref: Phys.Lett. B416 (1998) 129-136
We show that an effective field theory that includes non-standard couplings between the electroweak gauge bosons and the top and bottom quarks may yield negative contributions to both the S and T oblique radiative electroweak parameters. We find that that such an effective field theory provides a better fit to data than the standard model (the chi-squared per degree of freedom is half as large). We examine in some detail an illustrative model where the exchange of heavy scalars produces the correct type of non-standard couplings.