Formation and Deformation of the $\psi(3770)$

TL;DR

This paper investigates the complex structure of the $770)$ resonance using a unitarized effective Lagrangian approach, revealing two poles and insights into its formation near the $D^{+}D^{-}$ threshold.

Contribution

It introduces a non-Breit-Wigner analysis of the $770)$ resonance considering threshold effects and identifies two poles, advancing understanding of its nonperturbative properties.

Findings

Two poles found near the resonance amplitude.

Non-Breit-Wigner energy distribution characterized.

Effects of the $D^{+}D^{-}$ threshold on the resonance.

Abstract

The form of resonance line-shapes unveils information about its nonperturbative properties and formation mechanisms. Here, we study the non-Breit-Wigner energy distribution of the resonance $\psi (3770)$ using an unitarized effective Lagrangian approach, that includes the effect of the nearby threshold $D^{+}D^{-}$. Two poles are found in the second Riemann sheet near the resonance amplitude. We discuss the setting of the free parameters and possible effects contributing to the signal.