Search for the decay K_L-> pi^0 nu nubar

Abstract

We report on a search for the rare decay K_L -> pi^0 nu nubar in the KTeV experiment at Fermilab. We searched for two-photon events whose kinematics were consistent with an isolated pi^0 coming from the decay K_L -> pi^0 nu nubar. One candidate event was observed, which was consistent with the expected level of background. An upper limit on the branching ratio was determined to be B(K_L -> pi^0 nu nubar) < 1.6E-6 at the 90% confidence level.