First observation of $B^{+} \to D_s^{+}K^{+}K^{-}$ decays and a search for $B^{+} \to D_s^{+}\phi$ decays

A search for B$^{+}$ → D$_{s}^{+}$ K$^{+}$K$^{−}$ decays is performed using pp collision data corresponding to an integrated luminosity of 4.8 fb$^{−1}$, collected at centre-of-mass energies of 7, 8 and 13 TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be