Search for the Pair Production of Dark Particles $X$ with $K_L^0\to XX$, $X\to \gamma \gamma$

C. Lin, J. K. Ahn, J. M. Choi +39

We present the first search for the pair production of dark particles $X$ via $K_L^0\to XX$ with $X$ decaying into two photons using the data collected by the KOTO experiment. No s…