Search for the Decay $K_L^0\to {\pi }^0\nu \bar{\nu }$

We performed a search for the $K_L^0\to {\pi }^0\nu \bar{\nu }$ decay at the KEK 12-GeV proton synchrotron. No candidate events were observed. An upper limit on the branching ratio for the decay was set to be $6.7\times {10}^{-8}$ at the 90% confidence level.