Radiative and Dalitz decays of $Υ(1S)$ in the light of the ATOMKI X17 anomaly

Abstract

We study the radiative decay $Υ(1S)\to η_bγ$ and the Dalitz decay $Υ(1S)\to η_b e^+ e^-$ within the framework of the Covariant Confined Quark Model. We provide theoretical predictions for the hadronic form factor, the radiative decay constant, and the decay branching fractions. Within the Standard Model we predict $Γ(Υ(1S)\toη_b γ) = 9.3(9)\, \textrm{eV}$ and $Γ(Υ(1S)\toη_b e^+ e^-) = 4.8(5)\times 10^{-2}\, \textrm{eV}$. The contribution of the hypothetical ATOMKI $X17$ vector boson to the Dalitz channel is also investigated.