The recent observations of the purely leptonic decay $Ds to mu^+ u_{mu}$ and $tau^+ u_{tau}$ at CLEO-c and $B$ factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant $f_{D_s}$ differs from th
e most precise unquenched lattice QCD calculation by 4 $sigma$ level. Meanwhile, the measured ratio, ${cal BR}(Ds to mu^+ u_{mu})$ / ${cal BR}(Dp to mu^+ u_{mu})$, is larger than the standard model prediction at 2.0$sigma$ level. We discuss that the precise measurement of the ratio ${cal BR}(Ds to mu^+ u_{mu})$ / ${cal BR}(Dp to mu^+ u_{mu})$ at BES-III will shed light on the presence of new intermediate particles by comparing the theoretical predictions, especially, the predictions of high precise unquenched lattice QCD calculation.
In this paper, we calculate the decay rates of $D^+ to D^0 e^+ u$, $D^+_S to D^0 e^+ u$, $B^0_S to B^+ e^- bar{ u}$, $D^+_S to D^+ e^- e^+$ and $B^0_S to B^0 e^-e^+$ semileptonic decay processes, in which only the light quarks decay, while the heav
y flavors remain unchanged. The branching ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the Standard Model. We also estimate the sensitivities of the measurements of these rare decays at the future experiments, such as BES-III, super-$B$ and LHC-$b$.
This paper presents the results of searches for the flavor-changing neutral current, lepton-number-violating and lepton-flavor-violating processes in the charm mesons decays. Recent results from charged $D$ mesons decays to final states with dielectr
ons from CLEO-c are reported. The prospects of the searches for the rare charm decays at BES-III are also discussed.
Most recently, both BaBar and Belle experiments found evidences of neutral $D$ mixing. In this paper, we discuss the constraints on the strong phase difference in $D^0 to Kpi$ decay from the measurements of the mixing parameters, $y^prime$, $y_{CP}$
and $x$ at the $B$ factories. The sensitivity of the measurement of the mixing parameter $y$ is estimated in BES-III experiment at $psi(3770)$ peak. We also make an estimate on the measurements of the mixing rate $R_M$. Finally, the sensitivity of the strong phase difference at BES-III are obtained by using data near the $Dbar{D}$ threshold with CP tag technique at BES-III experiment.
