First Measurement of the Absolute Branching Fraction of η c → γ γ

M. Ablikim; Mikhail N. Achasov; P. Adlarson; X. Ai; R. Aliberti; A. Amoroso; Q. An; Y. Bai; Olga Bakina; Y. Ban; Yingying Ban; H. -R. Bao; V. Batozskaya; K. Begzsuren; N. Berger; M. Berlowski; M. Bertani; D. Bettoni; Fabrizio Bianchi; E. Bianco; A. Bortone; I. R. Boyko; Roy A. Briere; A. Brueggemann; H. Cai; H. Cai; M. H. Cai; Alessandro Calcaterra; G. F. Cao; G. F. Cao; Serkant Ali Cetin; X. Y. Chai; J. F. Chang; J. F. Chang; G. R. Che; G. R. Che; Yuzhi Che; C. H. Chen; Chao Chen; H. S. Chen; H. Y. Chen; H. Y. Chen; M. L. Chen; S. L. Chen; S. L. Chen; T. Chen; W. Chen; X. R. Chen; X. R. Chen; X. R. Chen; Y. B. Chen; Y. B. Chen; Z. K. Chen; J. Cheng; S.-K. Choi; X. Chu; G. Cibinetto; F. Cossio; J. Cottee Meldrum; H. L. Dai; H. L. Dai; J. P. Dai; A. Dbeyssi; R. E. de Boer; D. Dedovich; C. Q. Deng; C. Q. Deng; Z. Y. Deng; I. Denisenko; Marco Giovanni Maria Destefanis; F. De Mori; J. Dong; X. X. Ding; Y. X. Ding; Y. X. Ding; L. Y. Dong; L. Y. Dong; M. Y. Dong; M. C. Du; M. C. Du; S. X. Du; S. X. Du; X. L. Du; Y. Y. Duan; P. Egorov; Gaofeng Fan; G. F. Fan; J. J. Fan; Y. H. Fan; Jin Fang; Jin Fang; S. Fang; W. X. Fang; L. Fava; F. Feldbauer; Giulietto Felici; C. Q. Feng; C. Q. Feng; J. H. Feng; L. Feng

doi:10.1103/whyk-ykjw

First Measurement of the Absolute Branching Fraction of η c → γ γ

Physical Review Letters 2026 Open access

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Authors: M. Ablikim, Mikhail N. Achasov, P. Adlarson, X. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, Olga Bakina, Y. Ban, Yingying Ban, H. -R. Bao

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V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, Fabrizio Bianchi, E. Bianco, A. Bortone, I. R. Boyko, Roy A. Briere, A. Brueggemann, H. Cai, H. Cai, M. H. Cai, Alessandro Calcaterra, G. F. Cao, G. F. Cao, Serkant Ali Cetin, X. Y. Chai, J. F. Chang, J. F. Chang, G. R. Che, G. R. Che, Yuzhi Che, C. H. Chen, Chao Chen, H. S. Chen, H. Y. Chen, H. Y. Chen, M. L. Chen, S. L. Chen, S. L. Chen, T. Chen, W. Chen, X. R. Chen, X. R. Chen, X. R. Chen, Y. B. Chen, Y. B. Chen, Z. K. Chen, J. Cheng, S.-K. Choi, X. Chu, G. Cibinetto, F. Cossio, J. Cottee Meldrum, H. L. Dai, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, C. Q. Deng, C. Q. Deng, Z. Y. Deng, I. Denisenko, Marco Giovanni Maria Destefanis, F. De Mori, J. Dong, X. X. Ding, Y. X. Ding, Y. X. Ding, L. Y. Dong, L. Y. Dong, M. Y. Dong, M. C. Du, M. C. Du, S. X. Du, S. X. Du, X. L. Du, Y. Y. Duan, P. Egorov, Gaofeng Fan, G. F. Fan, J. J. Fan, Y. H. Fan, Jin Fang, Jin Fang, S. Fang, W. X. Fang, L. Fava, F. Feldbauer, Giulietto Felici, C. Q. Feng, C. Q. Feng, J. H. Feng, L. Feng

DOI: 10.1103/whyk-ykjw

Cited by: 0

References: 55

Abstract

We apply a tag-and-probe method to precisely measure the absolute branching fraction of the decay η_{c}→γγ with the BESIII experiment at BEPCII. Starting with a large initial sample of (2712.4±14.3)×10^{6} ψ(3686) events, a sample of 0.16×10^{6} η_{c} events is tagged via the golden channel ψ(3686)→π^{0}h_{c}, h_{c}→γη_{c}, effectively avoiding interference effects. The absolute branching fraction of η_{c}→γγ is measured for the first time to be B(η_{c}→γγ)=(2.45±0.48_{stat}±0.09_{syst})×10^{-4}. Using the world average value of the total width of the η_{c}, the partial decay width of η_{c}→γγ is calculated to be Γ(η_{c}→γγ)=(7.48±1.48_{stat}±0.30_{syst}) keV.

Fields of Study & Subjects

Quantum Chromodynamics and Particle Interactions Particle physics theoretical and experimental studies High-Energy Particle Collisions Research

Publication details

Journal / source: Physical Review Letters
Volume: 137
Issue: 7
Pages: 071802–071802
Publication date: 23 June 2026
Language: EN

References 55