Unified coupled-channel description for the five near-threshold structures ψ ( 3770 ) , G ( 3900 ) , R ( 3760 ) , R ( 3780 ) and R ( 3810 ) from e + e − annihilation
Ri-Qing Qian, Xiang Liu · Physical review. D/Physical review. D. · 2025
The recent observation of multiple near-threshold structures in e + e − annihilation—including ψ ( 3770 ) , G ( 3900 ) , R ( 3760 ) , R ( 3780 ) , and R ( 3810 ) —reveals limitations in existing models of charmonium and exotic hadrons. In this paper, we propose a unified coupled-channel description that simultaneously incorporates all five near-threshold structures using parameters constrained by hadron spectroscopy. Our model accurately reproduces the line shapes in both D D ¯ and nonopen-charm hadron (nOCH) channels, resolves the asymmetric profile of ψ ( 3770 ) , and produces the G ( 3900 ) bump. We identify the R ( 3780 ) as the dominant manifestation of ψ ( 3770 ) , attribute R ( 3760 ) to D D ¯ → nOCH rescattering and suggest that R ( 3810 ) arises from coupling between the ψ ( 1 D ) state and the h c π π channel. The significant non- D D ¯ decay of ψ ( 3770 ) is explained by its near-threshold position. This analysis provides a coherent, unquenched framework centered on a charmonium ψ ( 1 D ) core for near-threshold phenomena and offers a predictive approach extendable to bottomonium systems and future data from Belle II.