S and T parameters from a light nonstandard Higgs particle

We determine the contribution to the S and T parameters coming from extensions of the standard model featuring a light nonstandard-like Higgs particle. We neatly separate, using the Landau gauge, the contribution from the purely nonstandard Higgs sector, from the one due to the interplay of this sector with the standard model. If the nonstandard Higgs sector derives from a new type of strong dynamics, the formalism allows one to precisely link the intrinsic underlying contribution with the experimentally relevant parameters. © 2013 American Physical Society.