First Observation of B[superscript +] → D[subscript s][superscript +]K][superscript +]K[superscript −] Decays and a Search for B[superscript +] → D[subscript s][superscript +]ϕ Decays

A search for B[superscript +] → D[subscript s][superscript +] K[superscript +] K [superscript −] decays is performed using pp collision data corresponding to an integrated luminosity of 4.8 fb[superscript −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 B(B[superscript +] → D[superscript +][subscript s] K[superscript +]K[superscript −]) = (7.1 ± 0.5 ± 0.6 ± 0.7) × 10[superscript −6], where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode B[superscript +] → D[superscript +][subscript s][bar over D][superscript 0]. A search is also performed for the pure annihilation decay B[superscript +] → D[superscript +][subscript s] φ. No significant signal is observed and a limit of B(B[superscript +] → D[superscript +][subscript s] φ < 4.9 × 10{superscript −7] (4.2 × 10[superscript −7]) is set on the branching fraction at 95% (90%) confidence level. Keywords: B physics, Branching fraction, Hadron-Hadron scattering (experiments), Rare decayNational Science Foundation (U.S.