Search for an invisible vector boson from π⁰ decays at NA62

The search for an invisible vector boson from π⁰ decays at the NA62 experiment at CERN Super Proton Syncrotron (SPS) is discussed. Within the proposed models for physics beyond the SM, hidden sectors consisting of new, light, weakly-coupled particles are a particularly compelling possibility. Thanks to the high beam intensity, the extremely good performance of the photon detection systems, particle identification system and the detectors timing, NA62 is suited to search for these new particles. Here the search for a dark photon from π⁰ decays using the K⁺ → π⁺π⁰, π⁰ → A⁰γ decay chain is illustrated. The result from the analysis of a sub-sample of 2016 data is reported, corresponding to 1% of the full statistics collected in 2016-2018. A new upper limit on the π⁰ → A⁰γ branching ratio has been set as a function of the dark photon mass, thus producing a new upper limit on the dark photon coupling parameter [1].