Search for rare quark-annihilation decays, $B^{-}\to D_s^{(*)-}\varphi$

We report on searches for $B^{-}\to D_s^{-}\varphi$ and $B^{-}\to D_s^{*-}\varphi$. In the context of the standard model, these decays are expected to be highly suppressed since they proceed through annihilation of the $b$ and $\overline{u}$ quarks in the $B^{-}$ meson. Our results are based on $234\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions $\mathcal{B}(B^{-}\to D_s^{-}\varphi )<1.9\times {10}^{-6}$ and $\mathcal{B}(B^{-}\to D_s^{*-}\varphi )<1.2\times {10}^{-5}$. These results are consistent with standard model expectations.

Figure 1

Feynman diagram for $B^{-}\to D_s^{(*)-}\varphi$.

Figure 2

Distribution of ${\mathrm{m}}_{\mathrm{ES}}$ for (a) $B^{-}\to D_s^{-}\varphi$ and (b) $B^{-}\to D_s^{*-}\varphi$ candidates in the $|\Delta E|$ signal region. The superimposed curves are the result of the fits described in the text. The dashed curve is the background contribution and the solid curve is the sum of the signal and background components.

Figure 3

Likelihood from the fit in arbitrary units as a function of the number of signal events. (a) $B^{-}\to D_s^{-}\varphi$; (b) $B^{-}\to D_s^{*-}\varphi$.