Observation of the decay Bs0 → ηcϕ and evidence for Bs0 → ηcπ+π−

A study of Bs0 → ηcϕ and Bs0 → ηcπ+π− decays is performed using pp collision data corresponding to an integrated luminosity of 3.0 fb−1, collected with the LHCb detector in Run 1 of the LHC. The observation of the decay Bs0 → ηcϕ is reported, where the ηc meson is reconstructed in the pp¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p\overline{p} $$\end{document}, K+K−π+π−, π+π−π+π− and K+K−K+K− decay modes and the ϕ(1020) in the K+K− decay mode. The decay Bs0 → J/ψϕ is used as a normalisation channel. Evidence is also reported for the decay Bs0 → ηcπ+π−, where the ηc meson is reconstructed in the pp¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ p\overline{p} $$\end{document} decay mode, using the decay Bs0 → J/ψπ+π− as a normalisation channel. The measured branching fractions are ℬBs0→ηcϕ=5.01±0.53±0.27±0.63×10−4,ℬBs0→ηcπ+π−=1.76±0.59±0.12±0.29×10−4,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \begin{array}{l}\mathrm{\mathcal{B}}\left({B}_s^0\to {\eta}_c\phi \right)=\left(5.01\pm 0.53\pm 0.27\pm 0.63\right)\times {10}^{-4},\hfill \\ {}\mathrm{\mathcal{B}}\left({B}_s^0\to {\eta}_c{\pi}^{+}{\pi}^{-}\right)=\left(1.76\pm 0.59\pm 0.12\pm 0.29\right)\times {10}^{-4},\hfill \end{array} $$\end{document} where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions. [graphic not available: see fulltext]