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.