Observation of $e^+e^-\to\pi^0\pi^0\psi_2(3823)$

TL;DR

This paper reports the first observation of the process $e^+e^- o \pi^0\pi^0\\psi_2(3823)$ at energies from 4.23 to 4.70 GeV, measuring its cross section, mass, and setting an upper limit on its width.

Contribution

It presents the first observation of the neutral pion pair production with $\\psi_2(3823)$ in electron-positron collisions, confirming isospin symmetry and providing precise measurements of the state’s properties.

Findings

First observation of $e^+e^- o \\pi^0\\\pi^0\\\psi_2(3823)$ with 6.0 sigma significance.

Measured ratio of neutral to charged pion production is 0.57 ± 0.14 ± 0.05.

Mass of $\\psi_2(3823)$ is 3824.5 ± 2.4 ± 1.0 MeV/$c^2$; width is less than 18.8 MeV at 90% CL.

Abstract

Using a data sample corresponding to an integrated luminosity of 11.3 $\rm fb^{-1}$ collected at center-of-mass energies from $4.23$ to $4.70$~GeV with the BESIII detector, we observe the process $e^+e^-\to\pi^0\pi^0\psi_2(3823)$ for the first time with a statistical significance of $6.0\sigma$. The ratio of average cross sections for $e^+e^-\to\pi^0\pi^0\psi_2(3823)$ over $\pi^+\pi^-\psi_2(3823)$ is determined to be $\mathcal{R}=\frac{\sigma[e^+e^-\to\pi^0\pi^0\psi_2(3823)]}{\sigma[e^+e^-\to\pi^+\pi^-\psi_2(3823)]}=0.57\pm 0.14\pm0.05$, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the $\psi_2(3823)$ is measured to be $M[\psi_2(3823)]=3824.5\pm 2.4\pm 1.0$~MeV/$c^2$. Due to the limited statistics, the intrinsic width of the $\psi_2(3823)$ is measured as an upper limit of $18.8$~MeV at $90\%$ confidence level.