  The nature of dark matter remains a central question in particle physics,
cosmology, and astrophysics. The prevailing hypothesis postulates that dark
matter consists of particles that interact only weakly with Standard Model
particles. However, the knowledge of dark matter properties beyond these
interactions is limited. This study explores a scenario involving a dark photon
as a mediator between dark matter and the Standard Model, akin to the photon's
role in electromagnetism. Recent cosmological and experimental evidence impose
constraints on this scenario, focusing on results from direct detection
experiments such as PICO-60, XENON-1T, and PANDAX-4T. The results reveal severe
constraints, effectively closing the window for laboratory searches for dark
photons as mediators between the Standard Model and the dark sector (dark
electrons) in the secluded dark matter scenario. The findings underscore the
need for alternative explanations and offer fresh perspectives on the ongoing
quest to understand dark matter and its interactions since they are nearly
independent of the dark electron fraction content for the total dark matter.
This analysis significantly narrows down the parameter space for thermal dark
matter scenarios involving a dark photon portal, reinforcing the urgency of
exploring alternative models and designing new experiments to unravel the
mysteries surrounding the nature of dark matter.
