Search for the rare decays $B^{+}\to D^{(*)+}{K}_S^0$

We report on the search for the rare decays $B^{+}\to D^{(*)+}{K}_S^0$ in approximately $226\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We do not observe any significant signal and we set 90% confidence-level upper limits on the branching fractions, $\mathcal{B}(B^{+}\to D^{+}{K}^0)<0.5\times {10}^{-5}$ and $\mathcal{B}(B^{+}\to D^{*+}{K}^0)<0.9\times {10}^{-5}$.

Figure 1

Annihilation diagram for the decay $B^{+}\to D^{(*)+}{K}_S^0$ (left), tree diagram for $B^{+}\to D_s^{(*)+}{\pi }^0$ (center), and hadron-level diagram for a possible rescattering contribution to $B^{+}\to D^{(*)+}{K}_S^0$ via $B^{+}\to D_s^{(*)+}{\pi }^0$ (right).

Figure 2

Distribution of the discriminating variables $|\cos {\theta }_T|$ and $\mathcal{F}$ in the $B^{+}\to D^{+}{K}_S^0$ signal MC (histograms) and the off-resonance data (dots).

Figure 3

The $m_{\mathrm{ES}}$ distribution for the a) $B^{+}\to D^{+}{K}_S^0$ and b) $B^{+}\to D^{*+}{K}_S^0$ candidates within the $\Delta E$ signal band in data after all selection requirements. Combinatorial (full line) and peaking (dashed line) backgrounds are superimposed.