PreprintCC BY 4.0arXiv21 Sep 2026

Observation of η(2600) and Threshold Enhancements in the ΛΛ̅ System

BESIII Collaboration
M. Ablikim
M. N. Achasov
P. Adlarson
X. C. Ai
C. S. Akondi
R. Aliberti
A. Amoroso
Q. An
Y. H. An
Y. Bai
O. Bakina

732 more authors

Y. Ban
H. -R. Bao
X. L. Bao
V. Batozskaya
K. Begzsuren
N. Berger
M. Berlowski
M. B. Bertani
D. Bettoni
F. Bianchi
E. Bianco
A. Bortone
I. Boyko
R. A. Briere
A. Brueggemann
H. Cai
M. H. Cai
X. Cai
A. Calcaterra
G. F. Cao
N. Cao
S. A. Cetin
X. Y. Chai
J. F. Chang
T. T. Chang
G. R. Che
Y. Z. Che
C. H. Chen
Chao Chen
G. Chen
H. S. Chen
H. Y. Chen
M. L. Chen
S. J. Chen
S. M. Chen
T. Chen
W. Chen
X. R. Chen
X. T. Chen
X. Y. Chen
Y. B. Chen
Y. Q. Chen
Z. K. Chen
J. Cheng
L. N. Cheng
S. K. Choi
X. Chu
G. Cibinetto

60 listed; 744 in total.

Abstract

Using 2712.4 ± 14.3 million ψ(3686) events collected with the BESIII detector, the ΛΛ̅ system produced in ψ(3686) radiative decays is studied. A model-independent partial wave analysis reveals a significant threshold enhancement structure dominated by the ¹S₀ and ³P₀ partial waves, corresponding to J^PC = 0⁻⁺ and 0⁺⁺, respectively. In addition, a new pseudoscalar resonance, designated as η(2600), is observed in the ¹S₀ partial wave with a mass value consistent with the previously reported X(2600) state, which represents the heaviest light meson observed to date. These results enhance our understanding of baryon-antibaryon threshold dynamics and the pseudoscalar light hadron spectroscopy.

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BibTeX RIS

BibTeX

@misc{collaboration2026observation,
  title = {{Observation of $η(2600)$ and Threshold Enhancements in the $Λ\barΛ$ System}},
  author = {BESIII Collaboration and M. Ablikim and M. N. Achasov and P. Adlarson and X. C. Ai and C. S. Akondi and R. Aliberti and A. Amoroso and Q. An and Y. H. An and Y. Bai and O. Bakina and Y. Ban and H. -R. Bao and X. L. Bao and V. Batozskaya and K. Begzsuren and N. Berger and M. Berlowski and M. B. Bertani and D. Bettoni and F. Bianchi and E. Bianco and A. Bortone and I. Boyko and R. A. Briere and A. Brueggemann and H. Cai and M. H. Cai and X. Cai and A. Calcaterra and G. F. Cao and N. Cao and S. A. Cetin and X. Y. Chai and J. F. Chang and T. T. Chang and G. R. Che and Y. Z. Che and C. H. Chen and Chao Chen and G. Chen and H. S. Chen and H. Y. Chen and M. L. Chen and S. J. Chen and S. M. Chen and T. Chen and W. Chen and X. R. Chen and X. T. Chen and X. Y. Chen and Y. B. Chen and Y. Q. Chen and Z. K. Chen and J. Cheng and L. N. Cheng and S. K. Choi and X. Chu and G. Cibinetto},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.25158},
  eprint = {2609.25158},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.25158},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Observation of η(2600) and Threshold Enhancements in the ΛΛ̅ System
AU  - BESIII Collaboration
AU  - M. Ablikim
AU  - M. N. Achasov
AU  - P. Adlarson
AU  - X. C. Ai
AU  - C. S. Akondi
AU  - R. Aliberti
AU  - A. Amoroso
AU  - Q. An
AU  - Y. H. An
AU  - Y. Bai
AU  - O. Bakina
AU  - Y. Ban
AU  - H. -R. Bao
AU  - X. L. Bao
AU  - V. Batozskaya
AU  - K. Begzsuren
AU  - N. Berger
AU  - M. Berlowski
AU  - M. B. Bertani
AU  - D. Bettoni
AU  - F. Bianchi
AU  - E. Bianco
AU  - A. Bortone
AU  - I. Boyko
AU  - R. A. Briere
AU  - A. Brueggemann
AU  - H. Cai
AU  - M. H. Cai
AU  - X. Cai
AU  - A. Calcaterra
AU  - G. F. Cao
AU  - N. Cao
AU  - S. A. Cetin
AU  - X. Y. Chai
AU  - J. F. Chang
AU  - T. T. Chang
AU  - G. R. Che
AU  - Y. Z. Che
AU  - C. H. Chen
AU  - Chao Chen
AU  - G. Chen
AU  - H. S. Chen
AU  - H. Y. Chen
AU  - M. L. Chen
AU  - S. J. Chen
AU  - S. M. Chen
AU  - T. Chen
AU  - W. Chen
AU  - X. R. Chen
AU  - X. T. Chen
AU  - X. Y. Chen
AU  - Y. B. Chen
AU  - Y. Q. Chen
AU  - Z. K. Chen
AU  - J. Cheng
AU  - L. N. Cheng
AU  - S. K. Choi
AU  - X. Chu
AU  - G. Cibinetto
PY  - 2026
DA  - 2026/09/21
PB  - arXiv
DO  - 10.48550/arxiv.2609.25158
UR  - https://arxiv.org/abs/2609.25158
AB  - Using 2712.4 ± 14.3 million ψ(3686) events collected with the BESIII detector, the ΛΛ̅ system produced in ψ(3686) radiative decays is studied. A model-independent partial wave analysis reveals a significant threshold enhancement structure dominated by the ^1S_0 and ^3P_0 partial waves, corresponding to J^PC = 0^−+ and 0^++, respectively. In addition, a new pseudoscalar resonance, designated as η(2600), is observed in the ^1S_0 partial wave with a mass value consistent with the previously reported X(2600) state, which represents the heaviest light meson observed to date. These results enhance our understanding of baryon-antibaryon threshold dynamics and the pseudoscalar light hadron spectroscopy.
ER  -

Abstract

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