Dark Photon Searches Using Displaced Vertices at Low Energy 𝑒⁺𝑒⁻ Colliders

Figure 5

Number of dark photons from the process 𝐽/𝜓→𝜂^′𝛾^′ with decay paths larger than 1 cm and lower than 5 cm, as a function of 𝜖 and for various values of 𝑚_𝛾′. An integrated luminosity of 1 ab⁻¹ is considered.