Weak decays of Heavy mesons

Abstract

I explore the possibility of using heavy meson decays as probes for flavour changing neutral transitions (FCNC) $c\to u\gamma$ and $c\to ul^+l^-$. In the standard model, these are the most frequent FCN transitions among the quarks with charge $2/3e_0$. I predict the short and long distance contributions to the relevant heavy meson decays within the standard model and explore their sensitivity to different scenarios of physics beyond the standard model. The rare $B_c\to B_u^*\gamma$ decay is proposed as the most suitable case study of the $c\to u\gamma$ transition and is studied with the ISGW model. Its detection at the branching ratio much higher than $10^{-8}$ would signal new physics. Weak decays of charm mesons to a light meson and a photon or a charged lepton pair are also studied for this purpose. Their probabilities are found to be dominated by the long distance contributions and raise our hopes that they may be detected soon. A window of opportunity to probe the $c\to ul^+l^-$ transition is found in the decay $D\to \pi l^+l^-$, at the kinematical region of high di-lepton mass. In order to study the charm meson decays, I adapt the Heavy Meson Chiral Lagrangian approach and demonstrate for its applicability by predicting the charm meson nonleptonic decay rates.