Updated constraints on new physics in rare charm decays

Abstract

Motivated by recent experimental results on charm physics, we investigate implications of the updated constraints of new physics in rare charm meson decays. We first reconsider effects of the minimal supersymmetric standard model (MSSM) in $c\ensuremath{\rightarrow}u\ensuremath{\gamma}$ constrained by the recent experimental evidence on $\ensuremath{\Delta}{m}_{D}$ and find that, due to the dominance of long-distance physics, $D\ensuremath{\rightarrow}V\ensuremath{\gamma}$ decay rates cannot be modified by MSSM contributions. Then we consider effects of the extra heavy up vectorlike quark models on the decay spectrum of ${D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ and ${D}_{s}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decays. We find a possibility for the tiny increase of the differential decay rate in the region of large dilepton mass. The $R$-parity violating supersymmetric model can also modify short distance dynamics in $c\ensuremath{\rightarrow}u{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decays. We constrain relevant parameters using the current upper bound on the ${D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decay rate and investigate the impact of that constraint on the ${D}_{s}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ differential decay dilepton distribution. Present bounds still allow a small modification of the standard model differential decay rate distribution.