Search for invisible dark photon in γ e scattering at future lepton colliders

For the first time, the production of a massive dark photon (DP) in the γ e^- scattering at the future lepton colliders ILC, CLIC, and CEPC is examined. The invisible decay mode of the DP is addressed. We have studied both the unpolarized scattering and the collision of the Compton backscattered photons with the polarized electron. The missing energy distributions are shown. We have considered the wide range 1–1000 GeV of the DP mass m_A' . The excluded regions at the 95