Search for a light pseudoscalar particle in the decay $K^0_L \to π^0 π^0 X$

Y. C. Tung; Y. B. Hsiung; M. L. Wu; K. F. Chen; J. K. Ahn; Y. Akune; V. Baranov; J. Comfort; M. Doroshenko; Y. Fujioka; T. Inagaki; S. Ishibashi; N. Ishihara; H. Ishii; E. Iwai; T. Iwata; I. Kato; S. Kobayashi; 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; T. Nakano; H. Nanjo; J. Nix; T. Nomura; M. Nomachi; R. Ogata; H. Okuno; K. Omata; G. N. Perdue; S. Podolsky; K. Sakashita; T. Sasaki; N. Sasao; H. Sato; T. Sato; M. Sekimoto; T. Shinkawa; Y. Sugaya; A. Sugiyama; T. Sumida; S. Suzuki; Y. Tajima; S. Takita; Z. Tsamalaidze; T. Tsukamoto; Y. Wah; H. Watanabe; M. Yamaga; T. Yamanaka; H. Y. Yoshida; Y. Yoshimura; Y. Zheng

doi:10.1103/physrevlett.102.051802

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arXiv · 0810.4222

Search for a light pseudoscalar particle in the decay $K^0_L \to π^0 π^0 X$

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Abstract

We performed a search for a light pseudoscalar particle $X$ in the decay $K_L^0->pi0pi0X$, $X->γγ$ 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 $K_L^0->pi0pi0X$, $X->γγ$ of $2.4 \times 10^{-7}$ 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.

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Y. C. Tung, Y. B. Hsiung, M. L. Wu, K. F. Chen, J. K. Ahn, Y. Akune, V. Baranov, J. Comfort, M. Doroshenko, Y. Fujioka, T. Inagaki, S. Ishibashi, N. Ishihara, H. Ishii, E. Iwai, T. Iwata, I. Kato, S. Kobayashi, 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, T. Nakano, H. Nanjo, J. Nix, T. Nomura, M. Nomachi, R. Ogata, H. Okuno, K. Omata, G. N. Perdue, S. Podolsky, K. Sakashita, T. Sasaki, N. Sasao, H. Sato, T. Sato, M. Sekimoto, T. Shinkawa, Y. Sugaya, A. Sugiyama, T. Sumida, S. Suzuki, Y. Tajima, S. Takita, Z. Tsamalaidze, T. Tsukamoto, Y. Wah, H. Watanabe, M. Yamaga, T. Yamanaka, H. Y. Yoshida, Y. Yoshimura, Y. Zheng. 2009-02-06. Search for a light pseudoscalar particle in the decay $K^0_L \to π^0 π^0 X$. https://doi.org/10.1103/physrevlett.102.051802

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