Measurement of the B0 → K∗0e+e− branching fraction at low dilepton mass

The branching fraction of the rare decay B0 → K∗0e+e− in the dilepton mass region from 30 to 1000 MeV/c2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, at a centre-of-mass energy of 7 TeV. The decay mode B0 → J/ψ (e+e−)K∗0 is utilized as a normalization channel. The branching fraction \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^0}\to {K^{*0 }}{e^{+}}{e^{-}}} \right) $\end{document} is measured to be \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ \mathcal{B}{{\left( {{B^0}\to {K^{*0 }}{e^{+}}{e^{-}}} \right)}^{{30-1000\,{{\mathrm{MeV}} \left/ {{{c^2}}} \right.}}}}=\left( {3.1_{-0.8}^{+0.9 }{\,}_{-0.3}^{+0.2}\pm 0.2} \right)\times {10^{-7 }}, $\end{document}where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B0 → J/ψ K∗0 and J/ψ → e+e− branching fractions. [graphic not available: see fulltext]