Precision measurements of branching fractions for ψ′→π0J/ψ and ηJ/ψ

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We present a precision study of the ${\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}J/\ensuremath{\psi}$ and $\ensuremath{\eta}J/\ensuremath{\psi}$ decay modes. The measurements are obtained using $106\ifmmode\times\else\texttimes\fi{}{10}^{6}$ ${\ensuremath{\psi}}^{\ensuremath{'}}$ events accumulated with the BESIII detector at the BEPCII ${e}^{+}{e}^{\ensuremath{-}}$ collider operating at a center-of-mass energy corresponding to the ${\ensuremath{\psi}}^{\ensuremath{'}}$ mass. We obtain $\mathcal{B}({\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}J/\ensuremath{\psi})=(1.26\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $\mathcal{B}({\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\eta}J/\ensuremath{\psi})=(33.75\ifmmode\pm\else\textpm\fi{}0.17(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.86(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The branching fraction ratio $R=\frac{\mathcal{B}({\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}J/\ensuremath{\psi})}{\mathcal{B}({\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\eta}J/\ensuremath{\psi})}$ is determined to be $(3.74\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.04(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$. The precision of these measurements of $\mathcal{B}({\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}J/\ensuremath{\psi})$ and $R$ represent a significant improvement over previously published values.

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