Phenomenology of the Charm decays[HBNI Th125]

Abstract

The thesis gives a detailed phenomenological analysis of the decays of the charmed mesons. Depending on the final state decay products, two types of charm meson decays have been discussed, the hadronic two body pseudoscalar charm decays and the radiative charm decays. The second chapter is dedicated to a solid understanding of the branching ratios of the considerably large number of two-body pseudoscalar charm decays that have been accessed experimentally. A parametrization is proposed for explaining the same and fits to the existing branching ratios have been carried out. The fits are in better agreement with experiment than previous works of this kind. The annihilation and exchange diagrams as well as non factorizable corrections and final state interactions have been taken into account. The related form factors have been extracted with considerable caution. The work addresses some puzzles related to various ratios involving two body pseudoscalar modes and the issue of possible double counting is addressed in details. The third chapter is on the radiative charm meson decays. A short discussion on the well known long distance contamination in such decays is provided followed by a detailed descritption of the short distance calculation upto the next-to-leading order in QCD within the Standard Model. It is shown that under the influence of a left-right symmetry and an additional down-type isosinglet heavy vector-like quark, the short distance branching ratios can be enhanced to the same order as those due to long distance at the bare level itself. A possible observable called photon polarization, which is not subject to large alterations due to QCD corrections, is proposed for the identification of such new physics.