Does ψ(4660) exist?
Abstract
The nature of the vector charmoniumlike states ψ(4360) and ψ(4660) is controversial, and the existence of the ψ(4660) has been questioned: the BESIII measurement of e+e-→ Λc+Λ̅c- reveals a nearly flat line shape around 4.66 GeV with a nonzero value at threshold, in contrast to the near-threshold enhancement reported earlier by Belle. We address this puzzle in an S-wave coupled-channel framework for e+e- annihilation in √s∈ [4.0,5.0] GeV. The formalism includes the open-charm channels Λc+Λ̅c-, Ξc+Ξ̅c-, Ξc0Ξ̅c0 (via SU(3) symmetry), the inelastic ψ(2S)π+π- channel mediated by σ(500) and f0(980), and the bare ψ(4360) and ψ(4660) as the 4S and 5S excitations. Short-range contact potentials in the heavy-quark limit are used, and the amplitudes follow from solving the Lippmann-Schwinger equation. A combined fit to Belle and BESIII data on e+e-→ Λc+Λ̅c- and e+e-→ ψ(2S)π+π- yields two poles, at (4401.93 ± 16.96i) MeV and (4631.39± 62.96i) MeV, for the ψ(4360) and ψ(4660). Tracing the pole trajectories as the coupling to the bare states is switched off, we show that both poles originate from the bare 4S and 5S states strongly renormalized by coupled-channel dynamics. In particular, the ψ(4660) emerges as a broad resonance about 58~MeV above the Λc+Λ̅c- threshold; its flat line shape follows from this threshold interplay, providing evidence for its existence. Results are cutoff-robust.
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BibTeX
@misc{wang2026does,
title = {{Does $ψ(4660)$ exist?}},
author = {Xian-Chen Wang and Quanxing Ye and Qian Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.03320},
eprint = {2605.03320},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.03320},
}
RIS
TY - UNPB
TI - Does ψ(4660) exist?
AU - Xian-Chen Wang
AU - Quanxing Ye
AU - Qian Wang
PY - 2026
DA - 2026/10/10
PB - arXiv
DO - 10.48550/arxiv.2605.03320
UR - https://arxiv.org/abs/2605.03320
AB - The nature of the vector charmoniumlike states ψ(4360) and ψ(4660) is controversial, and the existence of the ψ(4660) has been questioned: the BESIII measurement of e^+e^-→ Λ_c^+Λ̅_c^- reveals a nearly flat line shape around 4.66 GeV with a nonzero value at threshold, in contrast to the near-threshold enhancement reported earlier by Belle. We address this puzzle in an S-wave coupled-channel framework for e^+e^- annihilation in √s∈ [4.0,5.0] GeV. The formalism includes the open-charm channels Λ_c^+Λ̅_c^-, Ξ_c^+Ξ̅_c^-, Ξ_c^0Ξ̅_c^0 (via SU(3) symmetry), the inelastic ψ(2S)π^+π^- channel mediated by σ(500) and f_0(980), and the bare ψ(4360) and ψ(4660) as the 4S and 5S excitations. Short-range contact potentials in the heavy-quark limit are used, and the amplitudes follow from solving the Lippmann-Schwinger equation. A combined fit to Belle and BESIII data on e^+e^-→ Λ_c^+Λ̅_c^- and e^+e^-→ ψ(2S)π^+π^- yields two poles, at (4401.93 ± 16.96i) MeV and (4631.39± 62.96i) MeV, for the ψ(4360) and ψ(4660). Tracing the pole trajectories as the coupling to the bare states is switched off, we show that both poles originate from the bare 4S and 5S states strongly renormalized by coupled-channel dynamics. In particular, the ψ(4660) emerges as a broad resonance about 58~MeV above the Λ_c^+Λ̅_c^- threshold; its flat line shape follows from this threshold interplay, providing evidence for its existence. Results are cutoff-robust.
ER -