Search for new light vector boson using J/\u03a8 at BESIII and Belle II

Kayoung Ban,Po-Yan Tseng,Yongsoo Jho,Youngjoon Kwon,Seokhee Park,Seong Chan Park

doi:10.1007/jhep04(2021)091

Abstract

We investigate various search strategies for light vector boson X in mathcal{O} (10) MeV mass range using J/Ψ associated channels at BESIII and Belle II: (i) J/Ψ → ηcX with 1010J/Ψs at BESIII, (ii) J/Ψ(ηc + X) + 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 ≤ |εe| ≤ 10−3 and 9 MeV ≤ mX ≤ 100MeV with 50 ab−1 at Belle II. This covers the favored signal region of 8Be* anomaly recently reported by Atomki experiment with mX ≃ 17 MeV.

Highlights

At Belle II, we use the channel e+e− → X + J/Ψ where the X bosons will leave signals with displaced vertices
We investigate various search strategies for light vector boson X in O(10) MeV mass range using J/Ψ associated channels at BESIII and Belle II: (i) J/Ψ → ηcX with 1010J/Ψs at BESIII, (ii) J/Ψ(ηc + X) + ̄ 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 ≤ |εe| ≤ 10−3 and 9 MeV ≤ mX ≤ 100MeV with 50 ab−1 at Belle II

Summary

Introduction

At Belle II, we use the channel e+e− → X + J/Ψ where the X bosons will leave signals with displaced vertices. Taking 17 MeV X boson for 8Be∗ anomaly to be real, we list, in table 2, the expected significances of J/Ψ → ηcX → ηce+e− with NJ/Ψ = 1011 at BESIII under the assumption of εc = εu, for various σm values.

Results

Conclusion