Spontaneous CP violation, sterile neutrino dark matter and leptogenesis

by Prof. Norimi Yokozaki (Zhejiang U.)

Friday 10 Oct 2025, 10:00 → 12:00 Asia/Tokyo

C205 (Department of Physics, Faculty of Science, U. Toyama)

We constructed a model for spontaneous CP symmetry breaking in
five-dimensional spacetime that has a potential to solve the strong CP
problem. To explain the nature of dark matter and the baryon asymmetry
of the universe, three right-handed neutrinos and B−L gauge
interaction are introduced in the bulk, in addition to the field
contents of the BentoBranco-Parada model. The wave-function profiles
in the fifth dimension can suppress dangerous operators allowed by
symmetries, and the scale of spontaneous CP symmetry breaking can be
sufficiently large to be consistent with thermal leptogenesis. In this
model, the lightest right-handed neutrino serves as dark matter with a
mass of O(10) keV. This small mass and the necessarily small mixing
are explained by the exponentially localized wave-function in the
fifth dimension due to a bulk mass term. The correct relic abundance
is achieved thanks to the B−L gauge interaction. The other heavy
right-handed neutrinos explain the observed neutrino mixing and the
baryon asymmetry of the universe through leptogenesis.