Search for the Rare Decay K(L) ---> pi0 pi0 gamma

The KTeV E799 experiment has conducted a search for the rare decay KL → π00γ via the topology KL → π0π0Dγ (where π0D → γe+e-). Due to Bose statistics of the π0 pair and the real nature of the photon, the KL → π0π0γ decay is restricted to proceed at lowest order by the CP conserving direct emission (DE) of an E2 electric quadrupole photon. The rate of this decay is interesting theoretically since chiral perturbation theory predicts that this process vanishes at level O(p4). Therefore, this mode probes chiral perturbation theory at O(p6). In this paper we report a determination of an upper limit of 2.43 x 10-7 (90% CL) for KL → π0π0γ. This is approximately a factor of 20 lower than previous results