Observation of the charmonium decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$

Abstract

Using $(2712.4\pm 14.3)\times 10^6$ $\psi (3686)$ events collected with the BESIII detector at the BEPCII collider, the decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$ is observed. We determine the product branching fraction $\mathcal{B}(J/\psi \to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to \gamma \gamma )=(5.23\pm 0.26_{stat.}\pm 0.30_{syst.})\times 10^{-6}$. This result is consistent with the LQCD calculation $(5.34\pm 0.16)\times 10^{-6}$ from HPQCD in 2023. By using the world-average values of $\mathcal{B}(J/\psi \to \gamma {\eta }_c)$ and the total decay width of ${\eta }_c$, the partial decay width $\Gamma ({\eta }_c\to \gamma \gamma )$ is determined to be $(11.30\pm 0.56_{stat.}\pm 0.66_{syst.}\pm 1.14_{ref.})\mathrm{keV}$, which deviates from the corresponding world-average value by $3.4\sigma$.

10 pages, 4 figures

References in corpus (22)

• Heavy quarkonium: progress, puzzles, and opportunities
• Charmonium
• Method for detector description transformation to Unity and application in BESIII
• TopoAna: A generic tool for the event type analysis of inclusive Monte-Carlo samples in high energy physics experiments
• Two Photon Decays of Charmonia from Lattice QCD
• Measurement of the gamma gamma* --> eta_c transition form factor
• Determination of the number of $\psi (3686)$ events taken at BESIII
• Kernel density estimation of a multidimensional efficiency profile
• Next-to-next-to-leading-order QCD corrections to hadronic width of pseudoscalar quarkonium
• Two Photon Transition Form Factor of $\bar{c}c$ Quarkonia
• Measurement of the integrated luminosity of the data collected at 3.773 GeV by BESIII from 2021 to 2024
• Study of charmonia in four-meson final states produced in two-photon collisions
• Observation of eta_c(1S) and eta_c(2S) decays to K+ K- pi+ pi- pi0 in two-photon interactions
• Precise determination of decay rates for ${\eta }_c\to \gamma \gamma$, $J/\psi \to \gamma {\eta }_c$ and $J/\psi \to {\eta }_c{e}^{+}{e}^{-}$ from lattice QCD
• The Glueball content of ${\eta }_c$
• Visualization for physics analysis improvement and applications in BESIII
• First-principle calculation of ${\eta }_c\to 2\gamma$ decay width from lattice QCD
• The heavy quarkonium inclusive decays using the principle of maximum conformality
• Ward Identity of the Vector Current and the Decay Rate of ${\eta }_c\to \gamma \gamma$ in Lattice QCD
• Exclusive quarkonium production or decay in soft gluon factorization
• A Lattice Study of the Two-photon Decay Widths for Scalar and Pseudo-scalar Charmonium
• Lattice study of $J/\psi \to \gamma {\eta }_c$ using a method without momentum extrapolation

Cited by in corpus (2)

• Exclusive photon-fusion production of even-spin resonances and exotic QED atoms in high-energy hadron collisions
• Study of the Magnetic Dipole Transition of $J/\psi \to \gamma {\eta }_c$ via ${\eta }_c\to p\bar{p}$