NA64 Status Report 2017

The experiment NA64 is aimed at a direct search for invisible decays of sub-GeV dark photons (A′). The main goal in 2016 was to probe a region of the A′ parameter space, particularly interesting for the explanation of the muon g − 2 anomaly. The status and results from two NA64 runs in July and October 2016, obtained, respectively, with 2.75×109 and 4×1010 accumulated electron on target are reported. A feasibility study of the search for the X → e+e− decay of a new light X boson, which could explain a recently observed excess of e+e− events from excited 8Be transitions is also presented.