Search for Dark Particles in $K_L^0\to \gamma X$ at the KOTO Experiment

T. Wu, Y. C. Tung, Y. B. Hsiung +24

We report a search for an invisible particle $X$ in the decay $K_L^0\to \gamma X$ ($X\to \text{invisible}$), where $X$ can be interpreted as a massless or massive dark photon. N…