S. Komatsu

Experimental study of the decay KL0→π0νν̄

The first dedicated search for the rare neutral-kaon decay

Study of the KL0→π0π0νν̄ decay

K_L^0\to\pi^0\nu\bar{\nu}

Search for the decay KL0→3γ

has been carried out in the E391a experiment at the KEK 12-GeV proton synchrotron. The final upper limit of 2.6

Experimental study of the decay K0(L) ---> pi0 nu nu-bar

\times 10^{-8}

Search for the decayKL0→3γ

at the 90% confidence level was set on the branching ratio for the decay.

Study of the K0(L) --> pi0 pi0 nu nu-bar decay

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.

Study of the K0L →π⁰π⁰νν¯decay

We performed a search for the decay

Study of theKL0→π0π0νν¯decay

K_L^0 \rightarrow 3\gamma

Search for the decay

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

K_L^0 \rightarrow 3\gamma

K_L^0 \rightarrow 3\gamma