Preprint

PUBDB-2025-00534

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Proposal of the KOTO II experiment

Ahn, J. K. ; Antonelli, A. ; Anzivino, G. ; Augustine, E. ; Bandiera, L. ; Bian, J. ; Brizioli, F. ; De Capua, S. ; Carini, G. ; Chobanova, V. ; D'Ambrosio, G. ; Dainton, J. B. ; Dőbrich, B.DESY* ; Fry, J. ; Gianoli, A. ; Glazov, A.DESY* ; Gonzalez, M. ; Gorbahn, M. ; Goudzovski, E. ; Homma, M. ; Hsiung, Y. B. ; Husek, T. ; Hutchcroft, D. ; Iyer, A. ; Jones, R. W. L. ; Katayama, M. ; Kawata, Y. ; Kim, E.-J. ; Kim, C. ; Komatsubara, T. ; Kotera, K. ; Kreps, M. ; Lamanna, G. ; Lazzeroni, C. ; Lezki, S. ; Lim, G. ; Lim, S. ; Lin, C. ; Mahmoudi, F. ; Martin, V. ; Massri, K. ; Matsumura, T. ; Montalto, L. ; Moulson, M. ; Nanjo, H. ; Needham, M. ; Neshatpour, S. ; Nomura, T. ; Ogawa, D. ; Ono, K. ; Pepe, M. ; Peruzzo, L. ; Pinzino, J. ; Protopopescu, D. ; Prouve, C. ; Reddel, T. ; Redeker, J. ; Rinaldi, D. ; Romagnoni, M. ; Romano, A. ; Rostomyan, A.DESY* ; Sanders, J. ; Martínez Santos, D. ; Sarra, I. ; Shaikhiev, A. ; Shiomi, K. ; Shiraishi, R. ; Soldani, M. ; Sozzi, M. ; Stillwell, B. ; Su, Y.-T. ; Swallow, J. ; Tajima, Y. ; Tomczak, A. ; Tung, Y.-C. ; Wah, Y. ; Wanke, R. ; Watanabe, H. ; Wendel, J. ; Wu, T. ; Wynd, M. ; Yang, G. ; KOTO Collaboration (Collaboration author)

2025

This record in other databases:  

Report No.: arXiv:2501.14827

Abstract: The KOTO II experiment is proposed to measure the branching ratio of the decay $K_L\to\pi^0\nu\bar{\nu}$ at J-PARC. With a beamline to extract long-lived neutral kaons at 5 degrees from a production target, the single event sensitivity of the decay is $8.5\times 10^{-13}$, which is much smaller than the Standard Model prediction $3\times 10^{-11}$. This allows searches for new physics beyond the Standard Model and the first discovery of the decay with a significance exceeding $5\sigma$. As the only experiment proposed in the world dedicated to rare kaon decays, KOTO II will be indispensable in the quest for a complete understanding of flavor dynamics in the quark sector. Moreover, by combining efforts from the kaon community worldwide, we plan to develop the KOTO II detector further and expand the physics reach of the experiment to include measurements of the branching ratio of the $K_L\to\pi^0\ell^+\ell^-$ decays, studies of other $K_L$ decays, and searches for dark photons, axions, and axion-like particles. KOTO II will therefore obtain a comprehensive understanding of $K_L$ decays, providing further constraints on new physics scenarios with existing $K^+$ results.

Note: Submitted to the J-PARC PAC. arXiv admin note: substantial text overlap with arXiv:2110.04462

---

Contributing Institute(s):

1. BELLE II Experiment (BELLE)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2025

---