arXiv subjects

Koji Shiomi

Publications and source records attributed to Koji Shiomi.

3 recordsLinked to original sources

arXiv2025

Proposal of the KOTO II experiment

The KOTO II experiment is proposed to measure the branching ratio of the decay $K_L\toπ^0ν\barν$ 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 $5σ$. 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 $K_L\toπ^0\ell^+\ell^-$ 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.

hep-ex↗

arXiv2021

Extension of the J-PARC Hadron Experimental Facility: Third White Paper

The J-PARC Hadron Experimental Facility was constructed with an aim to explore the origin and evolution of matter in the universe through the experiments with intense particle beams. In the past decade, many results on particle and nuclear physics have been obtained at the present facility. To expand the physics programs to unexplored regions never achieved, the extension project of the Hadron Experimental Facility has been extensively discussed. This white paper presents the physics of the extension of the Hadron Experimental Facility for resolving the issues in the fields of the strangeness nuclear physics, hadron physics, and flavor physics.

nucl-ex↗

arXiv2014

$K^{0}_{L}\rightarrow π^{0} ν\barν$ at KOTO

The KOTO experiment aims to discover the rare decay $K^{0}_{L}\rightarrow π^{0} ν\barν$ at J-PARC. This mode breaks the CP symmetry directly and is highly suppressed in the Standard Model. Thus the mode is sensitive to new physics, in particular to the models related to CP violation. We performed the first physics run in May 2013. Although the data taking was terminated after 100 hours due to an accident, the single event sensitivity for the $K^{0}_{L}\rightarrow π^{0} ν\barν$ decay reached $1.29\times10^{-8}$, which was comparable to the sensitivity of the prior experiment. We observed one candidate event while $0.36\pm0.16$ background events were expected.

hep-ex↗