Improved measurement of $ψ(3686)\to π^+π^- η$

Using a sample of $(2712.4 \pm 14.3) \times 10^6$ $ψ(3686)$ events collected with the BESIII detector, we perform a partial wave analysis of the decay $ψ(3686)\toπ^{+}π^{-}η$ with the $π^{+}π^{-}$ invariant mass in the $ρ(770)^0$ mass region, [0.3, 2.2] $\mathrm{GeV}/c^2$. 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 $ψ(3686)\toρ(770)^0η$ is determined to be $(1.34 \pm 0.03\pm0.13) \times 10^{-5}$. The $ψ(3686)\to a_{2}(1320)^{\pm}π^{\mp}$ decay is observed for the first time with a significance of $35.7σ$, and its partial branching fraction is measured to be $(2.13 \pm 0.05\pm0.32) \times 10^{-5}$. The $η$-$η^{\prime}$ pseudoscalar mixing angle $θ_P$ is then found to be $(-11.2 \pm 1.6\pm3.6)^\circ$ or $(-19.4\pm 3.1\pm5.7)^\circ$, where the first uncertainty is statistical and the second systematic.

Authors

Publication Details

Journal
arXiv (Cornell University)
Published
2026-10-27
DOI
https://doi.org/10.48550/arxiv.2610.37182
Primary Topic
Quantum Chromodynamics and Particle Interactions
Type
preprint
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preprint

Improved measurement of $ψ(3686)\to π^+π^- η$

W. X. Fang, Yuzhi Che, S. M. Chen, K. Begzsuren et al.
arXiv (Cornell University)
Quantum Chromodynamics and Particle Interactions
preprint

Improved measurement of $ψ(3686)\to π^+π^- η$

W. X. Fang, Yuzhi Che, S. M. Chen, K. Begzsuren, Niklaus Berger, V. Batozskaya, A. Calcaterra, G. F. Cao, S. S. Fang, D. Bettoni, Igor R. Boyko, H. L. Dai, Z. H. Duan, Xi Chu, S. J. Chen, G Cibinetto, S. K. Choi, E. Bianco, M. L. Chen, A. Brueggemann, Roy A. Briere, G. R. Che, A. Bortone, E. Di Fiore, X. C. Ai, Fabrizio Bianchi, A. G. Denig, D. Dedovich, M Destefanis, BESIII Collaboration, R. Aliberti, M. Y. Dong, F. De Mori, M. N. Achasov, M. Berlowski, M. C. Du, X. Y. Chai, S. X. Du, J. Cottee-Meldrum, S Gevrek Çetin, R. E. de Boer, F. Cossio, H. S. Chen, A. Amoroso, K. X. Fan, P Adlarson, M. Ablikim, M. H. Cai, M. Barbagiovanni, M. B. Bertani, M. S. Anderson, C. S. Akondi, X. L. Bao, Q. An, P. Egorov, A. Dbeyssi, O. Bakina, I. Denisenko, H. R. Bao, Y. H. An, D. Cabiati, Z. Y. Deng, L. Y. Dong, X. L. Du, Z. K. Chen, Y. Q. Chen, Jin Fang, J. J. Fan, H. Cai, G. F. Fan, J. Fang, J. P. Dai, J. Cheng, W. Chen, L. N. Cheng, J. F. Chang, Y. Bai, G. Chen, Y. Q. Du, Y. H. Fan, X. K. Cai, X. Dong, C. H. Chen, H. Y. Chen, T. Chen, N. Cao, X. X. Ding, Y. X. Ding, Z. J. Dong, X. C. Dai, Chao Chen, X. Y. Chen, Shaoxu Du, J. Dong, T. T. Chang, Y. Y. Duan
preprint en

Abstract

Using a sample of $(2712.4 \pm 14.3) \times 10^6$ $ψ(3686)$ events collected with the BESIII detector, we perform a partial wave analysis of the decay $ψ(3686)\toπ^{+}π^{-}η$ with the $π^{+}π^{-}$ invariant mass in the $ρ(770)^0$ mass region, [0.3, 2.2] $\mathrm{GeV}/c^2$. 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 $ψ(3686)\toρ(770)^0η$ is determined to be $(1.34 \pm 0.03\pm0.13) \times 10^{-5}$. The $ψ(3686)\to a_{2}(1320)^{\pm}π^{\mp}$ decay is observed for the first time with a significance of $35.7σ$, and its partial branching fraction is measured to be $(2.13 \pm 0.05\pm0.32) \times 10^{-5}$. The $η$-$η^{\prime}$ pseudoscalar mixing angle $θ_P$ is then found to be $(-11.2 \pm 1.6\pm3.6)^\circ$ or $(-19.4\pm 3.1\pm5.7)^\circ$, where the first uncertainty is statistical and the second systematic.

arXiv (Cornell University)
Quantum Chromodynamics and Particle Interactions
DOIOpen Access PDFOpenAlex
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