Searches for dark photon with the ATLAS detector at the LHC

Many extensions to the Standard Model (SM) introduce a hidden or dark sector (DS) to provide candidates for dark matter in the universe and an explanation to astrophysical observations such as the positron excess observed in the cosmic radiation flux. This hidden sector could rise from an additional U(1)d gauge symmetry. ATLAS (A Toroidal LHC Apparatus) searches for the gauge boson of the DS that could be either a massless or a massive dark photon that can kinetically mix with the SM photon, or couple to the Higgs sector via some mediators. If dark photons decay back to the SM with a significant branching ratio, we could either observe measurable deviations in some particular Higgs decay channels or new exotic signatures that would be accessible at the Large Hadron Collider (LHC) energies.