Search for new light vector boson using J/Ψ at BESIII and Belle II

Abstract

Abstract We investigate various search strategies for light vector boson X in O $$ \mathcal{O} $$ (10) MeV mass range using J/Ψ associated channels at BESIII and Belle II: (i) J/Ψ → η c X with 1010 J/Ψs at BESIII, (ii) J/Ψ(η c + X) + ℓ ℓ ¯ $$ \mathrm{\ell}\overline{\mathrm{\ell}} $$ production at Belle II, and (iii) J/Ψ + X with the displaced vertex in X → e + e − decay are analyzed and the future sensitivities at Belle II with 50 ab −1 luminosity are comprehensively studied. By requiring the displaced vertex to be within the beam pipe, the third method results in nearly background-free analysis, and the vector boson-electron coupling and the vector boson mass can be probed in the unprecedented range, 10 −4 ≤ |ε e | ≤ 10 −3 and 9 MeV ≤ m X ≤ 100MeV with 50 ab −1 at Belle II. This covers the favored signal region of 8Be* anomaly recently reported by Atomki experiment with m X ≃ 17 MeV.

Keywords

• Beyond Standard Model
• Gauge Symmetry