NA64 is a fixed target experiment at the CERN SPS aiming at a sensitive search for hidden sectors. In this seminar, we will present the experiment and our latest results on the search for a new sub-GeV vector gauge boson (A′) mediated dark matter (χ) production. The A′, called dark photon, could be generated in the reaction e−Z→e−ZA′ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay A′→χχ. The experimental signature of this process would be a clean event with an isolated electron and large missing energy in the detector. This allows us to set new limits on the γ−A′ mixing strength and constrain some parameter space for the most interesting light dark matter models. Results on the search for the visible A' -> e⁺e⁻ decays, as well as X→ e+e− decay of a new 17 MeV X boson, which could explain a recently observed anomaly in the 8Be transitions and a search for axion-like particles will be also discussed. We will conclude with the future prospects of the experiment which will resume data taking in 2021 after the CERN long shutdown.

Dr Paolo Crivelli is an Adjunct Professor at ETH Zurich and the deputy spokesperson of the NA64 experiment at CERN. He is an internationally acclaimed specialist in exotic atoms and dark matter. He investigates these by means of high-​precision experiments. He was awarded an ERC Consolidator Grant for his research.