Search for Rare and Forbidden Decays $D^{+}\to h^{\pm }{e}^{\mp }{e}^{+}$

Using $0.8\times {10}^6$ $D^{+}{D}^{-}$ pairs collected with the CLEO-c detector at the $\psi (3770)$ resonance, we have searched for flavor-changing neutral current and lepton-number-violating decays of $D^{+}$ mesons to final states with dielectrons. We find no indication of either, obtaining 90% confidence level upper limits of $\mathcal{B}(D^{+}\to {\pi }^{+}{e}^{+}{e}^{-})<7.4\times {10}^{-6}$, $\mathcal{B}(D^{+}\to {\pi }^{-}{e}^{+}{e}^{+})<3.6\times {10}^{-6}$, $\mathcal{B}(D^{+}\to K^{+}{e}^{+}{e}^{-})<6.2\times {10}^{-6}$, and $\mathcal{B}(D^{+}\to K^{-}{e}^{+}{e}^{+})<4.5\times {10}^{-6}$.

Figure 1

Scatter plots of $\Delta M_{\mathrm{bc}}$ vs $\Delta E$ obtained from data for each decay mode. The signal region, defined by $-20\mathrm{MeV}\le \Delta E<20\mathrm{MeV}$ and $-5\mathrm{MeV}\le \Delta M_{\mathrm{bc}}<5\mathrm{MeV}$, is shown as a box. The two contours for each mode enclose regions determined with signal MC simulations to contain 50% and 85% of signal events, respectively.