Search for $\chi_{c1}\to \pi^{+}\pi^{-}\eta_c$ via $\psi(3686)\to\gamma\chi_{c1}$

BESIII Collaboration; M. Ablikim; M. N. Achasov; P. Adlarson; X. C. Ai; R. Aliberti; A. Amoroso; Q. An; Y. Bai; O. Bakina; Y. Ban; H. -R. Bao; V. Batozskaya; K. Begzsuren; N. Berger; M. Berlowski; M. 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; 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. L. Chen; S. M. Chen; T. Chen; X. R. Chen; X. T. Chen; X. Y. Chen; Y. B. Chen; Y. Q. Chen; Z. J. Chen; Z. K. Chen; S. K. Choi; X. Chu; G. Cibinetto; F. Cossio; J. Cottee-Meldrum; J. J. Cui; H. L. Dai; J. P. Dai; A. Dbeyssi; R. E. de Boer; D. Dedovich; C. Q. Deng; Z. Y. Deng; A. Denig; I. Denysenko; M. Destefanis; F. De~Mori; B. Ding; X. X. Ding; Y. Ding; Y. X. Ding; J. Dong; L. Y. Dong; M. Y. Dong; X. Dong; M. C. Du; S. X. Du; Y. Y. Duan; P. Egorov; G. F. Fan; J. J. Fan; Y. H. Fan; J. Fang; S. S. Fang; W. X. Fang; Y. Q. Fang; R. Farinelli; L. Fava; F. Feldbauer; G. Felici; C. Q. Feng; J. H. Feng; L. Feng; Q. X. Feng; Y. T. Feng; M. Fritsch; C. D. Fu; J. L. Fu

arXiv · 2508.18601

Search for $\chi_{c1}\to \pi^{+}\pi^{-}\eta_c$ via $\psi(3686)\to\gamma\chi_{c1}$

BESIII Collaboration·M. Ablikim·M. N. Achasov·P. Adlarson·X. C. Ai·R. Aliberti·A. Amoroso·Q. An·Y. Bai·O. Bakina·Y. Ban·H. -R. Bao·V. Batozskaya·K. Begzsuren·N. Berger·M. Berlowski·M. 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·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. L. Chen·S. M. Chen·T. Chen·X. R. Chen·X. T. Chen·X. Y. Chen·Y. B. Chen·Y. Q. Chen·Z. J. Chen·Z. K. Chen·S. K. Choi·X. Chu·G. Cibinetto·F. Cossio·J. Cottee-Meldrum·J. J. Cui·H. L. Dai·J. P. Dai·A. Dbeyssi·R. E. de Boer·D. Dedovich·C. Q. Deng·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·F. De~Mori·B. Ding·X. X. Ding·Y. Ding·Y. X. Ding·J. Dong·L. Y. Dong·M. Y. Dong·X. Dong·M. C. Du·S. X. Du·Y. Y. Duan·P. Egorov·G. F. Fan·J. J. Fan·Y. H. Fan·J. Fang·S. S. Fang·W. X. Fang·Y. Q. Fang·R. Farinelli·L. Fava·F. Feldbauer·G. Felici·C. Q. Feng·J. H. Feng·L. Feng·Q. X. Feng·Y. T. Feng·M. Fritsch·C. D. Fu·J. L. Fu

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Abstract

Utilizing $(2712.4 \pm 14.3) \times 10^6$ $\psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we search for the hadronic transition process $\chi_{c1} \to \pi^+\pi^-\eta_c$ following the decay $\psi(3686)\to \gamma \chi_{c1}$. No significant signal is observed, and an upper limit of $\mathcal{B}(\chi_{c1}\to\pi^+\pi^-\eta_c)$ is determined to be $3.1 times 10^{-4}$~at 90\% confidence level, which is one order of magnitude more stringent than the previous measurement.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. 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, 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. L. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, X. Y. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, Z. K. Chen, S. K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. Cottee-Meldrum, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De~Mori, B. Ding, X. X. Ding, Y. Ding, Y. X. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Y. Y. Duan, P. Egorov, G. F. Fan, J. J. Fan, Y. H. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Q. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, L. Feng, Q. X. Feng, Y. T. Feng, M. Fritsch, C. D. Fu, J. L. Fu. 2025-08-26. Search for $\chi_{c1}\to \pi^{+}\pi^{-}\eta_c$ via $\psi(3686)\to\gamma\chi_{c1}$. https://arxiv.org/abs/2508.18601

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