Speaker
Description
The KOTO experiment has reported an excess of $K_L\to\pi^0\bar\nu\nu$ events above standard model expectations. New physics interpretations of an excess in this channel are constrained by the Grossman-Nir bound, but another possibility is that the observed events in fact originate from a different process entirely: a decay of the form $K_L\to\pi^0\phi$, where $\phi$ denotes one or more new invisible species. We introduce a set of fiducial models to study this scenario, and we examine the possibility that $\phi$ may also account for cosmological dark matter. We show that $\phi$ is in fact a natural dark matter candidate, and that it is readily produced non-thermally, particularly with a low reheating scale. We discuss astrophysical and terrestrial signatures that may allow further tests of this paradigm.
