Search for the rare decays $B^0\to D_s^{(*)+}{a}_{0(2)}^{-}$

We have searched for the decays $B^0\to D_s^{+}{a}_0^{-}$, $B^0\to D_s^{*+}{a}_0^{-}$, $B^0\to D_s^{+}{a}_2^{-}$ and $B^0\to D_s^{*+}{a}_2^{-}$ in a sample of about $230\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We find no evidence for these decays and set upper limits at 90% C.L. on the branching fractions: $\mathcal{B}(B^0\to D_s^{+}{a}_0^{-})<1.9\times {10}^{-5}$, $\mathcal{B}(B^0\to D_s^{*+}{a}_0^{-})<3.6\times {10}^{-5}$, $\mathcal{B}(B^0\to D_s^{+}{a}_2^{-})<1.9\times {10}^{-4}$, and $\mathcal{B}(B^0\to D_s^{*+}{a}_2^{-})<2.0\times {10}^{-4}$.

Figure 1

Top two diagrams: tree diagrams contributing to the decay amplitude of $B^0\to D^{(*)-}{a}_{0(2)}^{+}$ (including the $B^0{\overline{B}}^0$ mixing mediated part of the amplitude). Bottom diagram: tree diagram representing the decay amplitude of $B^0\to D_s^{(*)+}{a}_{0(2)}^{-}$.

Figure 2

Distributions of $m_{\mathrm{ES}}$ for $B^0\to D_s^{(*)+}{a}_{0(2)}^{-}$ candidates overlaid with the projection of the maximum-likelihood fit. Contributions from the three $D_s^{+}$ decay modes are shown with different hatching styles: $\varphi {\pi }^{+}$ is cross hatched, ${\overline{K}}^{*0}{K}^{+}$ is hatched, and $K_S^0{K}^{+}$ is white. The fit procedure and results are described in the text.

Figure 3

Likelihood functions of the fit for the $m_{\mathrm{ES}}$ distributions of the selected $B^0\to D_s^{(*)+}{a}_{0(2)}^{-}$ candidates. Solid curves represent the original likelihood scan from the fit, the dashed lines show the result of the convolution with the systematic errors Gaussian. Vertical lines indicate the 90% Bayesian C.L. upper limit value.