Observation of the Electromagnetic Dalitz Transition $h_c\to e^{+}{e}^{-}{\eta }_c$

Abstract

Using $(27.12\pm 0.14)\times 10^8$ $\psi (3686)$ decays and data samples of $e^{+}{e}^{-}$ collisions with $\sqrt{s}$ from 4.130 to 4.780~GeV collected with the BESIII detector, we report the first observation of the electromagnetic Dalitz transition $h_c\to e^{+}{e}^{-}{\eta }_c$ with a statistical significance of $5.4\sigma$. We measure the ratio of the branching fractions $\frac{\mathcal{B}(h_c\to e^{+}{e}^{-}{\eta }_c)}{\mathcal{B}(h_c\to \gamma {\eta }_c)}$ separately for the $h_c$ samples produced via $\psi (3686)\to {\pi }^0{h}_c$ and $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{h}_c$. The average ratio is determined to be $(0.59\pm 0.10(\text{stat.})\pm 0.04(\text{syst.}))\%$, where the uncertainty includes both statistical and systematic components.

References in corpus (23)

• Design and Construction of the BESIII Detector
• Higher Charmonia
• Future Physics Programme of BESIII
• Observation of a charged charmoniumlike structure Z_c(4020) and search for the Z_c(3900) in e+e- to pi+pi-h_c
• Precision measurement of the integrated luminosity of the data taken by BESIII at center of mass energies between 3.810 GeV and 4.600 GeV
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• Measurements of h_c(^1P_1) in psi' Decays
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• Precision Measurement of the Mass of the h_c(1P1) State of Charmonium
• Measurement of integrated luminosities at BESIII for data samples at center-of-mass energies between 4.0 and 4.6 GeV
• Observation of the ^1P_1 State of Charmonium
• Determination of the number of $\psi (3686)$ events taken at BESIII
• Improved measurement of the absolute branching fraction of $D^{+}\to {\bar{K}}^0{\mu }^{+}{\nu }_{\mu }$
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• First study of reaction ${\Xi }^{0}n\to {\Xi }^{-}p$ using ${\Xi }^0$-nucleus scattering at an electron-positron collider
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• Test of $CP$ Symmetry in Hyperon to Neutron Decays
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• Study of the $h_c$($1^1{P}_1$) meson via $\psi (2S)\to {\pi }^0{h}_c$ decays at BESIII
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• QCD analysis of the $P$-wave charmonium electromagnetic Dalitz decays $h_c\to {\eta }^{(\prime )}{\ell }^{+}{\ell }^{-}$