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Two-loop contributions to the [Beta] - [|Beta] mixing amplitude Fortin, Simon


It is known that the Standard Model, being a spontaneously broken gauge theory, violates the decoupling theorem. In practice, this means that amplitudes for low-energy processes grow without limit as the mass of fermions or scalars is made large. As a result of the recent determination of a lower bound of 90 GeV on the mass of the top quark and the general expectation of a large mass for the Higgs boson, this effect could lead to large higher order corrections to the observables of the theory. In this spirit, we calculate the two-loop corrections to the [Beta] - [|Beta] mixing amplitude in the two limits of a very large top quark mass or a very large Higgs mass. Analytical expressions are obtained for the leading terms. The results are found to be much smaller than what one would naively expect.

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