We show a simple mechanism for a dynamical CPT violation in the neutron sector. In particular, we show a CPT-violating see-saw mechanism, generating a Majorana mass and a CPT-violating mass for the neutron. CPT-violating see-saw involves a sterile partner of the neutron, living in a hidden sector, in which CPT is spontaneously broken. In particular, neutrons (antineutrons) can communicate with the hidden sector through nonperturbative quantum gravity effects called exotic instantons. Exotic instantons dynamically break R-parity, generating one effective vertex between the neutron and its sterile partner. In this way, we show how a small CPT-violating mass term for the neutron is naturally generated. This model can be tested in the next generation of experiments in neutron–antineutron physics. This strongly motivates researches of CPT-violating effects in neutron–antineutron physics as a test-bed for dynamical CPT-violations in SM.
Empirical inference on the Majorana mass of the ordinary neutrinos