Search for the decay $K_L^0 \rightarrow 3γ$

hep-ex

/ Authors

Y. C. Tung, Y. B. Hsiung, J. K. Ahn, Y. Akune, V. Baranov, K. F. Chen, J. Comfort, M. Doroshenko, Y. Fujioka, T. Inagaki

and 59 more authors

S. Ishibashi, N. Ishihara, H. Ishii, E. Iwai, T. Iwata, I. Kato, S. Kobayashi, S. Komatsu, T. K. Komatsubara, A. S. Kurilin, E. Kuzmin, A. Lednev, H. S. Lee, S. Y. Lee, G. Y. Lim, J. Ma, T. Matsumura, A. Moisseenko, H. Morii, T. Morimoto, Y. Nakajima, T. Nakano, H. Nanjo, N. Nishi

/ Abstract

We performed a search for the decay $K_L^0 \rightarrow 3γ$ 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 $K_L^0 \rightarrow 3γ$ proceeding via parity-violation, we obtained the single event sensitivity to be $(3.23\pm0.14)\times10^{-8}$, and set an upper limit on the branching ratio to be $7.4\times10^{-8}$ at the 90% confidence level. This is a factor of 3.2 improvement compared to the previous results. The results of $K_L^0 \rightarrow 3γ$ proceeding via parity-conservation were also presented in this paper.