First observation of the decays ${\bar{B}}_{(s)}^0\to D_s^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and ${\bar{B}}_s^0\to D_{s1}(2536{)}^{+}\ddot{I}{€}^{-}$

Abstract

The first observation of the decays ${\bar{B}}_s^0\to D_s^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and ${\bar{B}}^0\to D_s^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ are reported using an integrated luminosity of 1.0 fb${}^{-1}$ recorded by the LHCb experiment. The branching fractions, normalized with respect to ${\bar{B}}_s^0\to D_s^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and ${\bar{B}}_s^0\to D_s^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$, respectively, are measured to be {\br(\bar{B}^0_{s}\to D_s^+K^-π^+π^-)\over\br(\bar{B}^0_{s}\to D_s^+π^-π^+π^-)} &= (5.2\pm0.5\pm0.3)\times10^{-2}, {\br(\bar{B}^0\to D_s^+K^-π^+π^-)\over\br(\bar{B}^0_{s}\to D_s^+K^-^π^+π^-)} &= 0.54\pm0.07\pm0.07, where the first uncertainty is statistical and the second is systematic. The ${\bar{B}}_s^0\to D_s^{+}{K}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ decay is of particular interest as it can be used to measure the weak phase ${\hat{I}}^3$. First observation of the ${\bar{B}}_s^0\to D_{s1}(2536{)}^{+}\ddot{I}{€}^{-},D_{s1}^{+}\to D_s^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}$ decay is also presented, and its branching fraction relative to ${\bar{B}}_s^0\to D_s^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ is found to be {\br(\bar{B}^0_s\to D_{s1}(2536)^+π^-, D_{s1}^+\to D_s^+π^-π^+)\over\br(\bar{B}^0_{s}\to D_s^+π^-π^+π^-)} &= (4.0\pm1.0\pm0.4)\times10^{-3}.

17 pages, 7 figures