학술논문
Study of the $K_L \!\to\! \pi^0 \nu \overline{\nu}$ Decay at the J-PARC KOTO Experiment
Document Type
Working Paper
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.; Zaidenberg, L.
Source
Phys. Rev. Lett. 126, 121801 (2021)
Subject
Language
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)
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)