Measurement of ${\mathrm{\Gamma }}_{ee}\times {\mathcal{B}}_{\mu \mu }$ for $\psi (2S)$ meson

The product of the electronic width of the $\psi (2S)$ meson and the branching fraction of its decay to the muon pair was measured in the $e^{+}e^{-} \to \psi(2S) \to \mu^{+}\mu^{-}$ process using nine data sets corresponding to an integrated luminosity of about 6.5 pb${}^{-1}$ collected with the KEDR detector at the VEPP-4M electron-positron collider: $${\mathrm{\Gamma }}_{ee}\times {\mathcal{B}}_{\mu \mu }=19.3\pm 0.3\pm 0.5\text{ eV}\mathrm{.}$$ Adding the previous KEDR results on hadronic and leptonic channels, the values of the $\psi (2S)$ electronic width were obtained under two assumptions: either with the assumption of lepton universality $${\mathrm{\Gamma }}_{ee}=2.279\pm 0.015\pm 0.042\text{ keV}$$ or without it, summing up hadronic and three independent leptonic channels: $${\mathrm{\Gamma }}_{ee}=2.282\pm 0.015\pm 0.042\text{ keV}\mathrm{.}$$