First evidence for the annihilation decay mode $B^{+}\to D_s^{+}\varphi$

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