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

Abstract

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.

Comments: 10 pages, 3 figures, v2: clarifications and two references added, version published in Phys. Rev. D