Abstract:
We report on the recent activity of the NA64 experiment at the SPS of CERN. The NA64 experiment uses an active beam-dump setup to conduct missing energy searches with high-intensity lepton beams (e or mu).
Since 2016 several dedicated searches for new mediators between standard model and dark sector were performed, most notably a light vector boson A’ and a short-lived neutral boson X(17). The A’ was proposed as a possible explanation for magnetic-moment anomalies of muons. At NA64 it could be created in electron-on-target reactions e−Z→e−ZA′ and supposedly decay invisibly into lighter dark-sector particles (A′→χχbar). The X is motivated by an excess of e+e−-pairs in 8Be* excited state nuclear transitions. At NA64 it could be produced in bremsstrahlung interactions e−Z→e−ZX and decay into standard model leptons (X→e+e−).
Starting in 2021, the search for a dark portal was expanded with a dedicated setup using a muon beam at the M2 beamline at the SPS of CERN. In 2022, a pilot run using an e+ beam for resonant A’ production in our active target was performed.
We present an overview over the experimental setups and analysis strategies, as well as the updated results until 2022.