Dark Sector searches with electron and positron beams at NA64@CERN

Several astrophysical observations indicate that the majority of the mass of the Universe is made of a new type of matter, called Dark Matter, not interacting with light. DM may be composed of a dark sector of new particles, charged under a new U(1) gauge boson kinetically mixed with the ordinary photon, called dark photon. The NA64e experiment at CERN aims to produce and detect DS particles using a 100 GeV electron beam impinging on a thick active target (electromagnetic calorimeter). The detection of DS particles in NA64e occurs through the ``missing energy" technique. So far, NA64e sets the most competitive limits in the $1$ MeV $ < $ m$_\chi <$ $100$ MeV parameters space, with an accumulated statistic of 9.37$\cdot 10^{11}$ electrons on target. In conjunction with the ERC-funded project POKER, from 2022 NA64e started collecting data also with positron beams, to exploit the DS production yield enhancement due to the positron resonant annihilation process. This work presents the latest results of the NA64e measurements, both with electron and positrons beams.