First evidence for the annihilation decay mode $B^{+} \to D_{s}^{+} \phi$

Evidence for the hadronic annihilation decay mode $B^{+} \to D_s^{+}\phi$ is found with greater than $3\sigma$ significance. The branching fraction and \CP asymmetry are measured to be \begin{eqnarray} \mathcal{B}(B^{+} \to D_s^{+}\phi) &=& \left(1.87^{\,+1.25}_{\,-0.73}\,({\rm stat}) \pm 0.19\, ({\rm syst}) \pm 0.32\, ({\rm norm})\right) \times 10^{-6}, \nonumber\\ \mathcal{A}_{CP}(B^{+} \to D_s^{+}\phi) &=& -0.01 \pm 0.41\, ({\rm stat}) \pm 0.03\, ({\rm syst}). \nonumber \end{eqnarray} The last uncertainty on $\mathcal{B}(B^{+} \to D_s^{+}\phi)$ is from the branching fractions of the $B^+ \to D_s^+ \kern 0.2em\overline{\kern -0.2em D}{}^0$ normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes $B^{+}_{(c)} \to D^{+}_{(s)} K^{*0}$, $B^{+}_{(c)} \to D^{+}_{(s)} \kern 0.2em\overline{\kern -0.2em K}{}^{*0}$ and ${B_c^{+} \to D^{+}_{s}\phi}$, including the result ${\mathcal{B}(B^+ \to D^+ K^{*0})} < 1.8 \times 10^{-6}$ at the 90% credibility level.