$c\to u\gamma$ in the minimal supersymmetric standard model
  The minimal supersymmetric standard model (MSSM) with universal soft breaking terms has a negligible effect on the rare $c\to u\gamma$ decay rate. We therefore study a general model with non-universal soft breaking terms constrained by vacuum stability and the experimental upper bound on the mass difference of the neutral charm mesons. It turns out that gluino exchange can enhance the standard model rate by up to two orders of magnitudes; in contrast, the contributions from charginos and neutralinos remain at least an order of magnitude below the QCD corrected standard model rate. 
S. Prelovsek and D. Wyler