Measurement of the branching fraction of B0→ J/ψπ0 decays

The ratio of branching fractions between B0 → J/ψπ0 and B+ → J/ψK*+ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The measured value isBB0→J/ψπ0BB+→J/ψK∗+=1.153±0.053±0.048×10−2,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \frac{{\mathcal{B}}_{B^0\to J/\psi {\pi}^0}}{{\mathcal{B}}_{B^{+}\to J/\psi {K}^{\ast +}}}=\left(1.153\pm 0.053\pm 0.048\right)\times {10}^{-2}, $$\end{document} where the first uncertainty is statistical and the second is systematic. The branching fraction for B0 → J/ψπ0 decays is determined using the branching fraction of the normalisation channel, resulting inBB0→J/ψπ0=1.670±0.077±0.069±0.095×10−5,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\mathcal{B}}_{B^0\to J/\psi {\pi}^0}=\left(1.670\pm 0.077\pm 0.069\pm 0.095\right)\times {10}^{-5}, $$\end{document} where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date.