Effective lagrangian analysis of new interactions and flavour conservation

Abstract

New interactions with a scale Λ larger than the Fermi scale G F − 1 2 will manifest themselves at energies below Λ through small deviations from the standard model, which can be described by an effective lagrangian containing non-renormalizable SU(3) × SU(2) × U(1) invariant operators. We construct the first two terms of this lagrangian in an expansion in powers of 1/Λ and study systematically possible effects of new interactions such as anomalous magnetic moments, deviations from universality in weak interactions and rare processes. Among the flavour conserving processes the universality of the charged current weak interactions yields the strongest bound on the new interaction scale, Λ > 5 TeV, whereas flavour non-conserving processes imply the bound Λ > 3000 TeV. We derive conditions for natural flavour conservation. Although it cannot be excluded that all flavour changing operators are dynamically suppressed, this appears difficult to understand without a symmetry for which the standard electroweak theory seems to provide no hint. We emphasize the importance of searching for rare decays of D-mesons.