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Particle Data Group, Workman, R.L., Burkert, V.D., Crede, V., Klempt, E., Thoma, U., et al. (2022) Review of Particle Physics. Progress of Theoretical and Experimental Physics, 2022, Article ID: 083C01.

has been cited by the following article:

• TITLE: Searching for Neutral State in the Rare Decay J/ψ → e + e − ϕ

  AUTHORS: Ahmed Rashed

  KEYWORDS: Rare Decays, Dark Matter, Hadrons

  JOURNAL NAME: Journal of High Energy Physics, Gravitation and Cosmology, Vol.12 No.2, February 13, 2026

  ABSTRACT: We investigate the decay process J/ψ → e + e − ϕ , where the relatively clean electromagnetic (EM) transitions dominate at leading order at the tree level, while hadronic contributions arise only through hadronic loop transitions. The branching ratio of J/ψ → e + e − ϕ was estimated to be approximately 2.28 × 10-8 where the hadronic effects are negligible compared to the EM contributions. The upper limit on the branching fraction was set to be B( J/ψ → e + e − ϕ )<1.2× 10 −7 by BESIII collaboration. In this paper, we investigate the existence of a neutral state such as dark photon and dark Z . Our analysis shows that the constraints on the dark photon and dark Z are stringent in the way that large enhancement to the SM branching ratio up to the present experimental limit is not possible. Therefore, observing a signal for the dark photon and dark Z in this decay channel is changeable.