Search for KL→π0π0γγ and KL→π0π0X where X→γγ at the KOTO Experiment

J. Redeker; C. Lin; Y. W. Wah; J. K. Ahn; M. Gonzalez; K. Hanai; Y. B. Hsiung; T. Kato; E. J. Kim; T. K. Komatsubara; K. Kotera; S. K. Lee; G. Y. Lim; T. Matsumura; H. Nanjo; T. Nomura; T. Nunes; K. Ono; K. Shiomi; R. Shiraishi; Y. Tajima; Y. C. Tung; H. Watanabe; T. Wu; T. Yamanaka; H. Y. Yoshida

doi:10.1103/pt2h-99by

Search for K_L→π⁰π⁰γγ and K_L→π⁰π⁰X where X→γγ at the KOTO Experiment

J. Redeker
, C. Lin
, Y. W. Wah
, J. K. Ahn
, M. Gonzalez
, K. Hanai
, Y. B. Hsiung
, T. Kato
, E. J. Kim
, T. K. Komatsubara
, K. Kotera
, S. K. Lee
, G. Y. Lim
, T. Matsumura
, H. Nanjo
, T. Nomura
, T. Nunes
, K. Ono
, K. Shiomi
, R. Shiraishi

Y. Tajima, Y. C. Tung, H. Watanabe, T. Wu, T. Yamanaka, H. Y. Yoshida

Physics Education

The University of Chicago
National Changhua University of Education
Korea University
The University of Osaka
National Taiwan University
High Energy Accelerator Research Organization, Institute of Particle and Nuclear Physics
J-PARC Center
Jeonbuk National University
National Defense Academy of Japan
Yamagata University
National Kaohsiung Normal University

Research output: Contribution to journal › Journal article › peer-review

Abstract

We performed searches for K_L→π⁰π⁰X where X may be an axionlike particle that promptly decays to two photons, and the first search for K_L→π⁰π⁰γγ at the KOTO experiment using data taken in 2021. The search is performed for X mass in the range of 160–220 MeV/c². Three events were observed in the signal region, with two events near an X mass of 177 MeV/c². This result led to a range of upper limits on the branching ratio, BR(K_L→π⁰π⁰X) <(1−20)×10^-7 at the 95% confidence level (CL). No events were observed for the analysis of K_L→π⁰π⁰γγ, setting an upper limit on the branching ratio, BR(_KL→π⁰π⁰γγ) <1.69×10^-6 at the 95% CL.

Original language	English
Article number	051804
Journal	Physical Review Letters
Volume	137
Issue number	5
DOIs	https://doi.org/10.1103/pt2h-99by
State	Published - 2026.07.31

Access to Document

10.1103/pt2h-99by

Cite this

Redeker, J., Lin, C., Wah, Y. W., Ahn, J. K., Gonzalez, M., Hanai, K., Hsiung, Y. B., Kato, T., Kim, E. J., Komatsubara, T. K., Kotera, K., Lee, S. K., Lim, G. Y., Matsumura, T., Nanjo, H., Nomura, T., Nunes, T., Ono, K., Shiomi, K., ... Yoshida, H. Y. (2026). Search for K_L→π⁰π⁰γγ and K_L→π⁰π⁰X where X→γγ at the KOTO Experiment. Physical Review Letters, 137(5), Article 051804. https://doi.org/10.1103/pt2h-99by

@article{8c58acec995d4a57a32dabb09a91763c,

title = "Search for KL→π0π0γγ and KL→π0π0X where X→γγ at the KOTO Experiment",

abstract = "We performed searches for KL→π0π0X where X may be an axionlike particle that promptly decays to two photons, and the first search for KL→π0π0γγ at the KOTO experiment using data taken in 2021. The search is performed for X mass in the range of 160{\textendash}220 MeV/c2. Three events were observed in the signal region, with two events near an X mass of 177 MeV/c2. This result led to a range of upper limits on the branching ratio, BR(KL→π0π0X) <(1−20){\texttimes}10-7 at the 95\% confidence level (CL). No events were observed for the analysis of KL→π0π0γγ, setting an upper limit on the branching ratio, BR(KL→π0π0γγ) <1.69{\texttimes}10-6 at the 95\% CL.",

author = "J. Redeker and C. Lin and Wah, \{Y. W.\} and Ahn, \{J. K.\} and M. Gonzalez and K. Hanai and Hsiung, \{Y. B.\} and T. Kato and Kim, \{E. J.\} and Komatsubara, \{T. K.\} and K. Kotera and Lee, \{S. K.\} and Lim, \{G. Y.\} and T. Matsumura and H. Nanjo and T. Nomura and T. Nunes and K. Ono and K. Shiomi and R. Shiraishi and Y. Tajima and Tung, \{Y. C.\} and H. Watanabe and T. Wu and T. Yamanaka and Yoshida, \{H. Y.\}",

note = "Publisher Copyright: {\textcopyright} 2026 authors. Published by the American Physical Society.",

year = "2026",

month = jul,

day = "31",

doi = "10.1103/pt2h-99by",

language = "English",

volume = "137",

journal = "Physical Review Letters",

issn = "0031-9007",

number = "5",

}

Redeker, J, Lin, C, Wah, YW, Ahn, JK, Gonzalez, M, Hanai, K, Hsiung, YB, Kato, T, Kim, EJ, Komatsubara, TK, Kotera, K, Lee, SK, Lim, GY, Matsumura, T, Nanjo, H, Nomura, T, Nunes, T, Ono, K, Shiomi, K, Shiraishi, R, Tajima, Y, Tung, YC, Watanabe, H, Wu, T, Yamanaka, T & Yoshida, HY 2026, 'Search for K_L→π⁰π⁰γγ and K_L→π⁰π⁰X where X→γγ at the KOTO Experiment', Physical Review Letters, vol. 137, no. 5, 051804. https://doi.org/10.1103/pt2h-99by

TY - JOUR

T1 - Search for KL→π0π0γγ and KL→π0π0X where X→γγ at the KOTO Experiment

AU - Redeker, J.

AU - Lin, C.

AU - Wah, Y. W.

AU - Ahn, J. K.

AU - Gonzalez, M.

AU - Hanai, K.

AU - Hsiung, Y. B.

AU - Kato, T.

AU - Kim, E. J.

AU - Komatsubara, T. K.

AU - Kotera, K.

AU - Lee, S. K.

AU - Lim, G. Y.

AU - Matsumura, T.

AU - Nanjo, H.

AU - Nomura, T.

AU - Nunes, T.

AU - Ono, K.

AU - Shiomi, K.

AU - Shiraishi, R.

AU - Tajima, Y.

AU - Tung, Y. C.

AU - Watanabe, H.

AU - Wu, T.

AU - Yamanaka, T.

AU - Yoshida, H. Y.

PY - 2026/7/31

Y1 - 2026/7/31

N2 - We performed searches for KL→π0π0X where X may be an axionlike particle that promptly decays to two photons, and the first search for KL→π0π0γγ at the KOTO experiment using data taken in 2021. The search is performed for X mass in the range of 160–220 MeV/c2. Three events were observed in the signal region, with two events near an X mass of 177 MeV/c2. This result led to a range of upper limits on the branching ratio, BR(KL→π0π0X) <(1−20)×10-7 at the 95% confidence level (CL). No events were observed for the analysis of KL→π0π0γγ, setting an upper limit on the branching ratio, BR(KL→π0π0γγ) <1.69×10-6 at the 95% CL.

AB - We performed searches for KL→π0π0X where X may be an axionlike particle that promptly decays to two photons, and the first search for KL→π0π0γγ at the KOTO experiment using data taken in 2021. The search is performed for X mass in the range of 160–220 MeV/c2. Three events were observed in the signal region, with two events near an X mass of 177 MeV/c2. This result led to a range of upper limits on the branching ratio, BR(KL→π0π0X) <(1−20)×10-7 at the 95% confidence level (CL). No events were observed for the analysis of KL→π0π0γγ, setting an upper limit on the branching ratio, BR(KL→π0π0γγ) <1.69×10-6 at the 95% CL.

UR - https://www.scopus.com/pages/publications/105046715401

U2 - 10.1103/pt2h-99by

DO - 10.1103/pt2h-99by

M3 - Journal article

C2 - 42606497

AN - SCOPUS:105046715401

SN - 0031-9007

VL - 137

JO - Physical Review Letters

JF - Physical Review Letters

IS - 5

M1 - 051804

ER -

Search for K_L→π⁰π⁰γγ and K_L→π⁰π⁰X where X→γγ at the KOTO Experiment

Abstract

Access to Document

Other files and links

Fingerprint

Cite this