Observation of the hindered electromagnetic Dalitz decay $ψ(3686) \to e^+ e^- η_c$
Creators: name: BESIII Collaboration
name: Ablikim, M.
name: Achasov, M. N.
name: Adlarson, P.
name: Albrecht, M.
name: Aliberti, R.
name: Amoroso, A.
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name: An, Q.
name: Bai, X. H.
name: Bai, Y.
name: Bakina, O.
name: Ferroli, R. Baldini
name: Balossino, I.
name: Ban, Y.
name: Batozskaya, V.
name: Becker, D.
name: Begzsuren, K.
name: Berger, N.
name: Bertani, M.
name: Bettoni, D.
name: Bianchi, F.
name: Bloms, J.
name: Bortone, A.
name: Boyko, I.
name: Briere, R. A.
name: Brueggemann, A.
name: Cai, H.
name: Cai, X.
name: Calcaterra, A.
name: Cao, G. F.
name: Cao, N.
name: Cetin, S. A.
name: Chang, J. F.
name: Chang, W. L.
name: Chelkov, G.
name: Chen, C.
name: Chen, Chao
name: Chen, G.
name: Chen, H. S.
name: Chen, M. L.
name: Chen, S. J.
name: Chen, S. M.
name: Chen, T.
name: Chen, X. R.
name: Chen, X. T.
name: Chen, Y. B.
name: Chen, Z. J.
name: Cheng, W. S.
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name: Chu, X.
name: Cibinetto, G.
name: Cossio, F.
name: Cui, J. J.
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name: Dbeyssi, A.
name: de Boer, R. E.
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name: Denig, A.
name: Denysenko, I.
name: Destefanis, M.
name: De Mori, F.
name: Ding, Y.
name: Dong, J.
name: Dong, L. Y.
name: Dong, M. Y.
name: Dong, X.
name: Du, S. X.
name: Egorov, P.
name: Fan, Y. L.
name: Fang, J.
name: Fang, S. S.
name: Fang, W. X.
name: Fang, Y.
name: Farinelli, R.
name: Fava, L.
name: Feldbauer, F.
name: Felici, G.
name: Feng, C. Q.
name: Feng, J. H.
name: Fischer, K
name: Fritsch, M.
name: Fritzsch, C.
name: Fu, C. D.
name: Gao, H.
name: Gao, Y. N.
name: Gao, Yang
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name: Garzia, I.
name: Ge, P. T.
name: Ge, Z. W.
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name: Gersabeck, E. M.
name: Gilman, A
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name: Gong, L.
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name: Gradl, W.
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Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Using a data sample of $(448.1 \pm 2.9)\times10^6 ~ψ(3686)$ decays collected at an $e^+ e^-$ center-of-mass energy of $3.686~\rm{GeV}$ by the BESIII detector at BEPCII, we report an observation of the hindered electromagnetic Dalitz decay $ψ(3686) \to e^+ e^- η_c$ with a significance of $7.9σ$. The branching fraction is determined to be $\mathcal{B} (ψ(3686) \to e^+ e^- η_c) = (3.77 \pm 0.40_{\rm stat.} \pm 0.18_{\rm syst.})\times 10^{-5}$, agreeing well with the prediction of the vector meson dominance model. This is the first measurement of the electromagnetic Dalitz transition between the $ψ(3686)$ and the $η_c$, which provides new insight into the electromagnetic properties of this decay, and offers new opportunities to measure the absolute branching fractions of $η_c$ decays.
description: 8 pages, 2 figures