Search for dark photons in $\pi^0$ decays at NA48 and NA62

The NA48/2 experiment at CERN collected, between 2003 and 2004, $1.69 \times 10^{7}$ fully reconstructed $\pi^{0} \to \gamma e^{+}e^{-}$ in the kinematic range $m_{ee}$ > 10 MeV/$c^{2}$, with a negligible background contamination. The sample is analysed to search for the presence of dark photons (${A}'$) via the decay chain $\pi^{0} \to \gamma{A}', {A}' \to e^{+}e^{-}$. No signal has been observed, and the exclusion limits on space of the dark photon mass $m_{{A}'}$ and the mixing parameter $e^{2}$ are reported.