H. Watanabe

Search for the decay KL0→π0νν̄

We performed a search for the K L0-->pi0nu nu[over] 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 x 10(-8) at the 90% confidence level.We performed a search for the

Study of the KL0→π0π0νν̄ decay

K^0_L \to \pi^0 \nu \bar{\nu}

Search for the decay KL0→3γ

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

KL → π0νν ̄experiment at KEK 12-GeV PS - E391a -

6.7 \times 10^{-8}

KL → π0ηη experiment at KEK12-GeV PS — E391a

at the 90% confidence level.

Undoped CsI calorimeter for the experiment at KEK-PS

The rare decay K0(L) --> pi0 pi0 nu nu-bar was studied with the E391a detector at the KEK 12-GeV proton synchrotron. Based on 9.4 x 10^9 K0L decays, an upper limit of 8.1 x 10^{-7} was obtained for the branching fraction at 90% confidence level. We also set a limit on the K0(L) --> pi0 pi0 X (X --> invisible particles) process; the limit on the branching fraction varied from 7.0 x 10^{-7} to 4.0 x 10^{-5} for the mass of X ranging from 50 MeV/c^2 to 200 MeV/c^2.

First search for KL?p0p0??

We performed a search for the decay

New limit on the KL0-->pi0nunu decay rate

K_L^0 \rightarrow 3\gamma

New limit on the KL0?p0?? decay rate

with the E391a detector at KEK. In the data accumulated in 2005, no event was observed in the signal region. Based on the assumption of

KL --> pi0etaeta experiment at KEK12-GeV PS - E391a

K_L^0 \rightarrow 3\gamma