Searching for light dark matter through Positronium decay

A novel approach to detect light dark matter through the observation of a single photon in the decay of Positronium (Ps) is proposed. Branching ratio calculations indicate that light dark matter coupling to the Standard Model through a novel dark vector boson in the mass range m(A') = 10-500 keV with strength epsilon = 2 x 10(-5)-10(-8) is well above the previously computed Standard Model background decay Ps -> gamma(nu) over bar nu and could be sensitive to observation.