Observation of the {B}_s^0 → D*+D*− decay

Abstract

The first observation of the {B}_s^0 → D∗+D∗− decay and the measurement of its branching ratio relative to the B0→ D∗+D∗− decay are presented. The data sample used corresponds to an integrated luminosity of 9 fb−1 of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with more than 10 standard deviations and the time-integrated ratio of branching fractions is determined to beBBs0→D∗+D∗−BB0→D∗+D∗−=0.269±0.032±0.011±0.008,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\frac{\\mathcal{B}\\left({B}_s^0\ o {D}^{\\ast +}{D}^{\\ast -}\\right)}{\\mathcal{B}\\left({B}^0\ o {D}^{\\ast +}{D}^{\\ast -}\\right)}=0.269\\pm 0.032\\pm 0.011\\pm 0.008, $$\\end{document}where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio fs/fd. The {B}_s^0 → D*+D*− branching fraction is calculated to beBBs0→D∗+D∗−=2.15±0.26±0.09±0.06±0.16×10−4,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{B}\\left({B}_s^0\ o {D}^{\\ast +}{D}^{\\ast -}\\right)=\\left(2.15\\pm 0.26\\pm 0.09\\pm 0.06\\pm 0.16\\right)\ imes {10}^{-4}, $$\\end{document}where the fourth uncertainty is due to the B0→ D*+D*− branching fraction. These results are calculated using the average {B}_s^0 meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light {B}_s^0 eigenstate is considered.