Measurement of $\Gamma_{ee}(J/\psi)$ with KEDR detector

TL;DR

This paper reports a precise measurement of the $J/\psi$ meson's electronic width and related parameters using the KEDR detector, providing results consistent with previous experiments and refining the total width estimate.

Contribution

The study presents new measurements of the $J/\psi$ electronic width and related branching fractions with improved precision using the KEDR detector at VEPP-4M.

Findings

Measured $\Gamma_{ee}(J/\psi)$ as 5.550 keV with uncertainties.

Determined the product of $\Gamma_{ee}$ and branching fractions for hadrons and electrons.

Calculated the total $J/\psi$ width as 92.94 keV.

Abstract

The product of the electronic width of the $J/\psi$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $\Gamma_{ee}(J/\psi) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV}, $ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_\text{hadrons}(J/\psi) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV}, $ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_{ee}(J/\psi) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/\psi$ meson: $\Gamma = 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.