Study of the Magnetic Dipole Transition of $J/\psi \to \gamma {\eta }_c$ via ${\eta }_c\to p\bar{p}$

Abstract

Using $(10.087\pm 0.044)\times 10^9$ $J/\psi$ events collected with the BESIII detector at the $e^{+}{e}^{-}$ BEPCII collider, we present the first amplitude analysis of $J/\psi \to \gamma p\bar{p}$ with the $p\bar{p}$ invariant mass in the ${\eta }_c$ mass region $[2.70,3.05]$~GeV/$c^2$. The product branching fraction $\mathcal{B}(J/\psi \to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to p\bar{p})$ is precisely determined to be $(2.11\pm 0.02_{\mathrm{stat}}\pm 0.07_{\mathrm{syst}})\times 10^{-5}$. Combining with the product branching fractions $\mathcal{B}({\eta }_c\to p\bar{p})\times \mathcal{B}({\eta }_c\to \gamma \gamma )$ and $\mathcal{B}(J/\psi \to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to \gamma \gamma )$, the branching fractions of $\mathcal{B}(J/\psi \to \gamma {\eta }_c)$ and $\mathcal{B}({\eta }_c\to \gamma \gamma )$ are calculated to be $(2.29\pm 0.01_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}}\pm 0.18_{\mathrm{opbf}})\%$ and $(2.28\pm 0.01_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}}\pm 0.18_{\mathrm{opbf}})\times 10^{-4}$, respectively, which are consistent with the latest lattice quantum chromodynamics calculations. Here, opbf is the uncertainty from the other product branching fractions used in the calculation.

11 Pages, 3 figures, submit to PRL

References in corpus (15)

• Highly Improved Staggered Quarks on the Lattice, with Applications to Charm Physics
• Charmonium spectrum and their electromagnetic transitions with higher multipole contributions
• Exotic and excited-state radiative transitions in charmonium from lattice QCD
• Number of $J/\psi$ events at BESIII
• Two Photon Decays of Charmonia from Lattice QCD
• Charmonium properties from lattice QCD + QED: hyperfine splitting, $J/\psi$ leptonic width, charm quark mass and $a_{\mu }^c$
• Next-to-next-to-leading-order QCD corrections to hadronic width of pseudoscalar quarkonium
• Two Photon Transition Form Factor of $\bar{c}c$ Quarkonia
• 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
• First-principle calculation of ${\eta }_c\to 2\gamma$ decay width from lattice QCD
• Ward Identity of the Vector Current and the Decay Rate of ${\eta }_c\to \gamma \gamma$ in Lattice QCD
• A Lattice Study of the Two-photon Decay Widths for Scalar and Pseudo-scalar Charmonium
• Observation of the charmonium decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$
• Lattice study of $J/\psi \to \gamma {\eta }_c$ using a method without momentum extrapolation
• Line shape and the experimental determination of the $J/\psi \to \gamma {\eta }_c$ branching fraction