Physics Beyond the Standard Model with the NA62 Experiment at CERN

The NA62 experiment at CERN is a high-intensity kaon decay experiment with a very broad physics program. Between 2016 and 2018, it collected the world’s largest dataset of K+ decays, which led to the first measurement of the branching ratio of the rare K+ → π+νν (PNN) decay, observed with a significance of 3.4σ. At the same time, several other new-physics (NP) studies are carried out. For example, the experiment is very active in the search for lepton-flavour/number-violating kaon decays, the most recent result concerning the K+ → µ-νe+e+ channel. Moreover, limits were recently set on the existence of evidence of a dark (pseudo-) scalar in the PNN dataset and hidden-sector mediators are sought in the K+ → π+e+e+e-e- channel. In 2021, the experiment was run in beam-dump mode for the first time. This allows for new searches for exotic particles — for instance, a massive dark photon which decays into a µ+µ- pair is sought.