Non-Standard Physics in Leptonic and Semileptonic Decays of Charmed Mesons
Abstract
Recent measurements of the branching fraction for Ds -> l nu disagree with the Standard Model expectation, which relies on calculations of fDs from lattice QCD. This paper uses recent preliminary measurements from CLEO and a new preliminary lattice-QCD result from this conference to update the significance of the discrepancy. The "fDs puzzle" stands now at 3.5sigma, with sigma predominantly from the statistical uncertainty of the experiments. New physics scenarios that could solve the puzzle would also lead to non-Standard amplitudes mediating the semileptonic decays D -> K l nu. This paper shows where the new amplitudes enter the differential rate and outlines where lattice QCD calculations are needed to confront recent and forthcoming measurements.