Improved measurement of ψ(3686)→ π⁺π^- η

@misc{collaboration2026improved,
  title = {{Improved measurement of $ψ(3686)\to π^+π^- η$}},
  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 M. S. Anderson and Y. Bai and O. Bakina and H. R. Bao and X. L. Bao and M. Barbagiovanni 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 D. Cabiati 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},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.37182},
  eprint = {2610.37182},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.37182},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Improved measurement of ψ(3686)→ π^+π^- η
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  - M. S. Anderson
AU  - Y. Bai
AU  - O. Bakina
AU  - H. R. Bao
AU  - X. L. Bao
AU  - M. Barbagiovanni
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  - D. Cabiati
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
PY  - 2026
DA  - 2026/10/27
PB  - arXiv
DO  - 10.48550/arxiv.2610.37182
UR  - https://arxiv.org/abs/2610.37182
AB  - Using a sample of (2712.4 ± 14.3) × 10^6 ψ(3686) events collected with the BESIII detector, we perform a partial wave analysis of the decay ψ(3686)→π^+π^−η with the π^+π^− invariant mass in the ρ(770)^0 mass region, [0.3, 2.2] GeV/c^2. The cross section line-shape around the ψ(3686) resonance is measured using energy-scan data sets, enabling the estimation of continuum contribution and its interference with the ψ(3686) resonance. The branching fraction of ψ(3686)→ρ(770)^0η is determined to be (1.34 ± 0.03±0.13) × 10^−5. The ψ(3686)→ a_2(1320)^±π^∓ decay is observed for the first time with a significance of 35.7σ, and its partial branching fraction is measured to be (2.13 ± 0.05±0.32) × 10^−5. The η-η^′ pseudoscalar mixing angle θ_P is then found to be (−11.2 ± 1.6±3.6)^∘ or (−19.4± 3.1±5.7)^∘, where the first uncertainty is statistical and the second systematic.
ER  -