Speaker: Cristina Lazzeroni (University of Birmingham)

The main aim of the proposed KOTO II experiment at JPARC is the measurement of the ultra-rare decay KL to pi0 nu nu.

This decay is heavily suppressed and its branching is very well predicted by the SM (3x 10-11 with about 2% uncertainty), thereby exhibiting an exceptional sensitivity to new physics.

The design includes a new beamline with a 5-degree extraction angle, and a new detector with a 12-meter-long signal decay region and a 3-meter diameter calorimeter.

A discovery of the KL to pi0 nu nu decay with 5σ significance is achievable for the SM value of the branching ratio.

The design, expected performance, and current status of the KOTO II experiment will be presented.