1. Study of the $K_L \!\to\! \pi^0 \nu \overline{\nu}$ Decay at the J-PARC KOTO Experiment
- Author
-
KOTO Collaboration, Ahn, J. K., Beckford, B., Campbell, M., Chen, S. H., Comfort, J., Dona, K., Farrington, M. S., Hanai, K., Hara, N., Haraguchi, H., Hsiung, Y. B., Hutcheson, M., Inagaki, T., Isoe, M., Kamiji, I., Kato, T., Kim, E. J., Kim, J. L., Kim, H. M., Komatsubara, T. K., Kotera, K., Lee, S. K., Lee, J. W., Lim, G. Y., Lin, Q. S., Lin, C., Luo, Y., Mari, T., Masuda, T., Matsumura, T., Mcfarland, D., McNeal, N., Miyazaki, K., Murayama, R., Nakagiri, K., Nanjo, H., Nishimiya, H., Noichi, Y., Nomura, T., Nunes, T., Ohsugi, M., Okuno, H., Redeker, J. C., Sanchez, J., Sasaki, M., Sasao, N., Sato, T., Sato, K., Sato, Y., Shimizu, N., Shimogawa, T., Shinkawa, T., Shinohara, S., Shiomi, K., Shiraishi, R., Su, S., Sugiyama, Y., Suzuki, S., Tajima, Y., Taylor, M., Tecchio, M., Togawa, M., Toyoda, T., Tung, Y. -C., Vuong, Q. H., Wah, Y. W., Watanabe, H., Yamanaka, T., Yoshida, H. Y., and Zaidenberg, L.
- Subjects
High Energy Physics - Experiment - Abstract
The rare decay $K_L \!\to\! \pi^0 \nu \overline{\nu}$ was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of $( 7.20 \pm 0.05_{\rm stat} \pm 0.66_{\rm syst} ) \times 10^{-10}$, three candidate events were observed in the signal region. After unveiling them, contaminations from $K^{\pm}$ and scattered $K_L$ decays were studied, and the total number of background events was estimated to be $1.22 \pm 0.26$. We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of $4.9 \times 10^{-9}$ on the branching fraction of $K_L \!\to\! \pi^0 \nu \overline{\nu}$ at the 90% confidence level., Comment: 6 pages, 5 figures; published version, no change in the results. Fig. 2 and Fig. 4 were revised. In Fig. 5, the plot of the $P_{t}$ versus ${Z_{\mathrm{vtx}}}$ of the beam-halo $K_L\!\to\!2\gamma$ background events was added as Fig. 5 (b)
- Published
- 2020
- Full Text
- View/download PDF