Precision measurements of branching fractions for $ \psi'\to\pi^0 J\psi$ and $\eta J\psi$

TL;DR

This paper reports precise measurements of the branching fractions for $oldsymbol{ ext{ψ'} o ext{π}^0 ext{J/ψ}}$ and $oldsymbol{ ext{η} ext{J/ψ}}$ decays, improving the accuracy of these fundamental parameters in charmonium physics.

Contribution

The study provides the most precise measurements to date of the branching fractions for these decay modes, refining previous experimental results.

Findings

Branching fraction for $ ext{ψ'} o ext{π}^0 ext{J/ψ}$ is $(1.26 imes 10^{-3})$ with uncertainties.

Branching fraction for $ ext{ψ'} o ext{η} ext{J/ψ}$ is $(33.75 imes 10^{-3})$ with uncertainties.

The ratio $R$ of the two branching fractions is $(3.74 imes 10^{-2})$, with improved precision.

Abstract

We present a precision study of the $\psip\to\pi^0 J/\psi$ and $\eta J/\psi$ decay modes. The measurements are obtained using $106\times10^6$ $\psi'$ events accumulated with the BESIII detector at the BEPCII $\ee$ collider operating at a center-of-mass energy corresponding to the $\psip$ mass. We obtain $\mathcal{B}(\psip\to\pi^0 J/\psi)=(1.26\pm0.02{\rm (stat.)}\pm0.03{\rm (syst.)})\times 10^{-3}$ and $\mathcal{B}(\psip\to\eta J/\psi)=(33.75\pm0.17{\rm (stat.)}\pm0.86{\rm (syst.)})\times 10^{-3}$. The branching fraction ratio $R=\frac{\mathcal{B}(\psip\to\pi^0 J/\psi)}{\mathcal{B}(\psip\to\eta J/\psi)}$ is determined to be $(3.74\pm0.06 {\rm(stat.)}\pm0.04 {\rm(syst.)})\times 10^{-2}$. The precision of these measurements of $\mathcal{B}(\psip\to\pi^{0} J/\psi)$ and $R$ represent a significant improvement over previously published values.