I. Kato

Experimental study of the decay KL0→π0νν̄

The first dedicated search for the rare neutral-kaon decay

Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X.

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

Search for the Decay K L-0 --> pi0nunu []

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

Search for a Light Pseudoscalar Particle in the DecayKL0→π0π0X

\times 10^{-8}

Search for the decay KL0→π0νν̄

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

Study of the KL0→π0π0νν̄ decay

We performed a search for a light pseudoscalar particle X in the decay K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/c;{2} was suggested by the HyperCP experiment. We found no evidence for X and set an upper limit on the product branching ratio for K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma of 2.4x10;{-7} at the 90% confidence level. Upper limits on the branching ratios in the mass region of X from 194.3 to 219.3 MeV/c;{2} are also presented.

Search for the decay KL0→3γ

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

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

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

Search for the decayKL0→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

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

6.7 \times 10^{-8}