Search for the decay $K_S\to {\pi }^0\gamma \gamma$

Abstract

A search for the decay $K_S\to {\pi }^0\gamma \gamma$ has been made using the NA48 detector at the CERN SPS. Using data collected in 1999 during a 40-hour run with a high-intensity $K_S$ beam, an upper limit for the branching ratio $BR(K_S\toπ^0γγ, z\ge 0.2)<3.3\times\nolinebreak 10^{-7}$ has been obtained at 90% confidence level, where $z=m_{\gamma \gamma }^2/m_{K_0}^2$.

12 pages, 4 figures; Submitted to Phys. Lett. B