New precision measurement of the $J/\psi$- and $\psi'$ -meson masses

TL;DR

This paper reports a highly precise measurement of the $J/ar{psi}$ and $ar{psi'}$ meson masses using resonant depolarization at VEPP-4M, achieving accuracy three times better than previous experiments.

Contribution

The study introduces a new high-precision measurement technique for meson masses employing resonant depolarization, significantly improving accuracy over prior results.

Findings

Measured $J/\psi$ mass as 3096.917 ± 0.010 ± 0.007 MeV

Measured $\psi'$ mass as 3686.111 ± 0.025 ± 0.009 MeV

Achieved relative measurement accuracy of 4×10^{-6} for $J/\psi$ and 7×10^{-6} for $\psi'$

Abstract

A new high precision measurement of the $J/\psi$- and $\psi'$-meson masses has been performed at the VEPP-4M collider using the KEDR detector. The resonant depolarization method has been employed for the absolute calibration of the beam energy. The following mass values have been obtained: $M_{J/\psi} = 3096.917 \pm 0.010 \pm 0.007$ MeV, $M_{\psi'} = 3686.111 \pm 0.025 \pm 0.009$ MeV. The relative measurement accuracy has reached $4. 10^{-6}$ for $J/\psi$ and $7. 10^{-6}$ for $\psi'$, approximately 3 times better than in the previous precise experiments.