Observation of the decay Bs0\u2009\u2192\u2009\u03b7c\u03d5 and evidence for Bs0\u2009\u2192\u2009\u03b7c\u03c0+\u03c0\u2212

Abstract

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 poverline{p} , 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 poverline{p} decay mode, using the decay Bs0 → J/ψπ+π− as a normalisation channel. The measured branching fractions areℬBs0→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}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\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.