Electronic width of the $\psi(3770)$ resonance interfering with the background

Methods for extracting the $\psi(3770)\to e^+e^-$ decay width from the data on the reaction cross section $e^+e^-\to D\bar D$ are discussed. Attention is drawn to the absence of the generally accepted method for determining $\Gamma_{\psi(3770)e^+e^-}$ in the presence of interference between the contributions of the $\psi(3770)$ resonance and background. It is shown that the model for the experimentally measured $D$ meson form factor, which satisfies the requirement of the Watson theorem and takes into account the contribution of the complex of the mixed $\psi(3770)$ and $\psi(2S)$ resonances, allows uniquely determine the value of $\Gamma_{\psi(3770)e^+e^-}$ by fitting. The $\Gamma_{\psi(3770)e^+ e^-}$ values found from the data processing are compared with the estimates in the potential models.