Search for production of an invisible dark photon in $\pi^0$ decays

International audienceThe results of a search for π$^{0}$ decays to a photon and an invisible massive dark photon at the NA62 experiment at the CERN SPS are reported. From a total of 4.12 × 10$^{8}$ tagged π$^{0}$ mesons, no signal is observed. Assuming a kinetic-mixing interaction, limits are set on the dark photon coupling to the ordinary photon as a function of the dark photon mass, improving on previous searches in the mass range 60–110 MeV/c$^{2}$. The present results are interpreted in terms of an upper limit of the branching ratio of the electro-weak decay $ {\pi}^0\to \gamma \nu \overline{\nu} $ , improving the current limit by more than three orders of magnitude