Exploring the threshold behavior and implications on the nature of Y(4260) and $Z_c(3900)$

TL;DR

This paper investigates the nature of Y(4260) and Zc(3900) by analyzing decay modes and threshold behaviors, highlighting the role of triangle singularities and suggesting radiative decays as probes for D(*)D̄ S-wave scattering.

Contribution

It introduces a detailed analysis of Y(4260)'s decay modes considering molecular and coupling scenarios, emphasizing the impact of triangle singularities on threshold phenomena.

Findings

Threshold enhancements and cusp structures can occur without genuine resonances.

Triangle singularities significantly influence decay amplitude behaviors.

Radiative decay modes are promising for studying D(*)D̄ S-wave interactions.

Abstract

By assuming that Y(4260) either is a $D_1\bar{D}$ molecular state, or has sizeable couplings with $D_0 \bar{D}^*$ and $D_1^\prime \bar{D}$, we investigate several decay modes of Y(4260). Under the special kinematic configurations, triangle singularity (TS) may occur in the rescattering amplitude, which will significantly change the threshold behavior. Obvious threshold enhancements or narrow cusp structures appear quite naturally without introducing a genuine resonance. We emphasize that the radiative decay modes may be useful for studying $D^{(*)}\bar{D}$ $S$-wave scattering.