Improved branching-fraction measurements of $B_{(s)}^0\to K_S^0{h}^{+}{h}^{{}^{\prime }-}$ decays and first observation of $B_s^0\to K_S^0{K}^{+}{K}^{-}$

Abstract

This paper presents a study of the charmless three-body decays $B_{(s)}^0\to K_{\mathrm{S}}^0{h}^{+}{h}^{\prime -}$ (where $h^{(\prime )}=\ddot{I}€,K$), using a sample of $pp$ collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9\mbox{\,fb}^{-1}$. The decay $B_s^0\to K_{\mathrm{S}}^0{K}^{+}{K}^{-}$ is observed for the first time, and the following ratios of branching fractions are measured: \begin{alignat*}{6} &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.578 &&\pm 0.007 &&\pm 0.017\,, &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.1363 &&\pm 0.0035 &&\pm 0.0051\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} π^+π^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.269 &&\pm 0.011 &&\pm 0.015 && \pm 0.008\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.0303 &&\pm 0.0041 &&\pm 0.0025 && \pm 0.0009\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 1.818 &&\pm 0.021 &&\pm 0.031 && \pm 0.056\,, \end{alignat*} where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the $B_s^0$ and $B^0$ mesons, respectively.

All figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/3621 (LHCb public pages)