Line shape of \psi(3770) in e^+e^-\to D\bar D

TL;DR

This paper analyzes the interference effects in the 770 resonance region of e+e- to Dar D reactions, emphasizing the importance of using amplitudes that satisfy elastic unitarity to accurately determine resonance parameters.

Contribution

It highlights the necessity of employing unitarity-compliant amplitudes and compares different models to better understand the 770 resonance shape and parameters.

Findings

Interference effects significantly influence 770 resonance parameters.

Model choice impacts the extracted resonance parameters.

Comparisons with non-Dar D channels help constrain models.

Abstract

Interference phenomena observed in the $\psi(3770)$ resonance region in the reactions $e^+e^-$ $\to$ $ D\bar D$ are analyzed. To avoid ambiguities in the determination of the $\psi(3770)$ resonance parameters, when analyzing data between the $D\bar D$ and $D\bar D\pi$ thresholds, the amplitudes satisfying the elastic unitarity requirement should be used. In the lack of information on the $P$ wave of $D\bar D$ elastic scattering, the $\psi(3770)$ parameters, determined by fitting the $e^+e^-$ $\to $ $D\bar D$ data, can essentially depend on the model used for the total contribution of the resonance and background. The selection of the models can be toughened by comparing their predictions with the relevant data on the shape of the $\psi(3770)$ peak in the non-$D\bar D$ channels $e^+e^-$ $\to $ $\gamma\chi_{c0}$, $J/\psi\eta$, $\phi\eta$, etc.