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Production of leptonium in heavy quarkonium decays

School of Physics, Shandong University, Jinan, Shandong 250100, China

^*Contact author: zyh329@mail.sdu.edu.cn
^†Contact author: jiangjun87@sdu.edu.cn

Phys. Rev. D 112, 056030 – Published 23 September, 2025

DOI: https://doi.org/10.1103/h57h-4ssj

Abstract

Lepton pairs with opposite charges can form bound states known as “leptonium” through quantum electrodynamic interactions. Heavy quarkonia such as $J / ψ$ are abundantly produced at facilities like BESIII and the future Super Tau-Charm Facility (STCF). In this work, we investigate leptonium production in heavy quarkonium decays, specifically focusing on the processes $Q ⟶ (l_{1}^{+} l_{2}^{-}) [n] + γ$ ( $l_{1, 2} = τ$ , $μ$ , $e$ ) and $Q ⟶ (l_{1}^{+} l_{2}^{-}) [n] + l_{1}^{-} l_{2}^{+}$ . Here, $Q$ denotes the heavy quarkonium $J / ψ$ or $ϒ$ , while $n = {{}^{1}S}_{0}$ or ${}^{3}{S_{1}}$ corresponds to para-leptonium and ortho-leptonium, respectively. With an annual production of $3.4 \times 10^{12} J / ψ$ events at STCF, there is significant potential to observe positronium $(e^{+} e^{-})$ , muonium $(μ^{+} e^{-})$ , and dimuonium $(μ^{+} μ^{-})$ . In particular, the ortho-dimuonium $(μ^{+} μ^{-}) [^{3} S_{1}]$ may be discovered at the future STCF, with an inclusive branching fraction of $Br (J / ψ ⟶ (μ^{+} μ^{-}) [^{3} S_{1}] + X) = 1.5 \times 10^{- 12}$ .

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Phys. Rev. D 112, 056030– Published 23 September, 2025

Vol. 112, Iss. 5 — 1 September 2025

Received 6 May 2025
Accepted 27 August 2025

DOI: https://doi.org/10.1103/h57h-4ssj

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Production of leptonium in heavy quarkonium decays

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