Observation of the {textrm{B}}_{textrm{s}}^0 → χc1(3872)π+π− decay

Abstract

The first observation of the {B}_s^0 → (χc1(3872) → J/ψπ+π−)π+π− decay is reported using proton-proton collision data, corresponding to integrated luminosities of 1, 2 and 6 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ratio of branching fractions relative to the {B}_s^0 → (ψ(2S) → J/ψπ+π−)π+π− decay is measured to beBBs0→χc13872π+π−×Bχc13872→J/ψπ+π−BBs0→ψ2Sπ+π−×Bψ2S→J/ψπ+π−=6.8±1.1±0.2×10−2,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\frac{\\mathcal{B}\\left({B}_s^0\ o {\\chi}_{c1}(3872){\\pi}^{+}{\\pi}^{-}\\right)\ imes \\mathcal{B}\\left({\\chi}_{c1}(3872)\ o J/\\psi {\\pi}^{+}{\\pi}^{-}\\right)}{\\mathcal{B}\\left({B}_s^0\ o \\psi (2S){\\pi}^{+}{\\pi}^{-}\\right)\ imes \\mathcal{B}\\left(\\psi (2S)\ o J/\\psi {\\pi}^{+}{\\pi}^{-}\\right)}=\\left(6.8\\pm 1.1\\pm 0.2\\right)\ imes {10}^{-2}, $$\\end{document}where the first uncertainty is statistical and the second systematic. The mass spectrum of the π+π− system recoiling against the χc1(3872) meson exhibits a large contribution from {B}_s^0 → χc1(3872) (f0(980) → π+π−) decays.