Rare Kaon Decay To Missing Energy: Implications Of The Na62 Result For A Z ' Model

Meson decays offer a good opportunity to probe new physics. The rare kaon decay K+ -> pi(+) nu(nu) over bar is one of the cleanest of them and, for this reason, is rather sensitive to new physics, in particular, vector mediators. The NA62 Collaboration, running a fixed-target experiment at CERN, recently reported an unprecedented sensitivity to this decay, namely a branching fraction of BR(K+ -> pi(+) nu(nu) over bar) = (11(-3.5)(+4.0)) x 10(-11) at 68% C.L. Vector mediators that couple to neutrinos may yield a sizeable contribution to this decay. Motivated by the new measurement, we interpret this result in the context of a concrete Z0 model, and put our findings into perspective with the correlated K-L -> pi(0)nu(nu) over bar decay measured by the KOTO Collaboration, current, and future colliders, namely the High-Luminosity and High-Energy Large Hadron Collider.