Study of $B_{(s)}^0\to K_{\mathrm{S}}^0{h}^{+}{h}^{\prime -}$ decays with first observation of $B_s^0\to K_{\mathrm{S}}^0{K}^{\pm }\ddot{I}{€}^{\mp }$ and $B_s^0\to K_{\mathrm{S}}^0\ddot{I}{€}^{+}\ddot{I}{€}^{-}$

Abstract

A search for charmless three-body decays of $B^0$ and $B_s^0$ mesons with a $K_{\mathrm{S}}^0$ meson in the final state is performed using the $pp$ collision data, corresponding to an integrated luminosity of $1.0\,\mbox{fb}^{-1}$, collected at a centre-of-mass energy of $7\mathrm{Te}\mathrm{V}$ recorded by the LHCb experiment. Branching fractions of the $B_{(s)}^0\to K_{\mathrm{S}}^0{h}^{+}{h}^{\prime -}$ decay modes ($h^{(\prime )}=\ddot{I}€,K$), relative to the well measured $B^0\to K_{\mathrm{S}}^0\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ decay, are obtained. First observation of the decay modes $B_s^0\to K_{\mathrm{S}}^0{K}^{\pm }\ddot{I}{€}^{\mp }$ and $B_s^0\to K_{\mathrm{S}}^0\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and confirmation of the decay $B^0\to K_{\mathrm{S}}^0{K}^{\pm }\ddot{I}{€}^{\mp }$ are reported. The following relative branching fraction measurements or limits are obtained \begin{eqnarray*} \nonumber \frac{{\cal B}(B^0 \to K_{\rm S}^0 K^{\pm} π^{\mp})}{{\cal B}(B^0 \to K_{\rm S}^0 π^{+} π^{-})} &=& 0.128 \pm 0.017 \, ({\rm stat.}) \pm 0.009 \, ({\rm syst.}) \,, \\ \nonumber \frac{{\cal B}(B^0 \to K_{\rm S}^0 K^{+} K^{-} )}{{\cal B}(B^0 \to K_{\rm S}^0 π^{+} π^{-})} &=& 0.385 \pm 0.031 \, ({\rm stat.}) \pm 0.023 \, ({\rm syst.}) \,, \\ \nonumber \frac{{\cal B}(B_s^0 \to K_{\rm S}^0 π^{+} π^{-} )}{{\cal B}(B^0 \to K_{\rm S}^0 π^{+} π^{-})} &=& 0.29\phantom{0} \pm 0.06\phantom{0} \, ({\rm stat.}) \pm 0.03\phantom{0} \, ({\rm syst.}) \pm 0.02 \, (f_s/f_d) \,, \\ \nonumber \frac{{\cal B}(B_s^0 \to K_{\rm S}^0 K^{\pm} π^{\mp})}{{\cal B}(B^0 \to K_{\rm S}^0 π^{+} π^{-})} &=& 1.48\phantom{0} \pm 0.12\phantom{0} \, ({\rm stat.}) \pm 0.08\phantom{0} \, ({\rm syst.}) \pm 0.12 \, (f_s/f_d) \,, \\ \nonumber \frac{{\cal B}(B_s^0 \to K_{\rm S}^0 K^{+} K^{-} )}{{\cal B}(B^0 \to K_{\rm S}^0 π^{+} π^{-})} &\in& [0.004;0.068] \; {\rm at \;\; 90\% \; CL} \,. \end{eqnarray*}

18 pages, 4 figures, published in JHEP. Changes in v2 are minor changes to the text and the presentation of the figures following suggestions from journal referees