CPT TEST IN NEUTRON-ANTINEUTRON TRANSITIONS

Abstract

Transitions n 4 A1 would violate B (baryon) and B L (baryon minus lepton) numbers by two units. Although direct violations of baryon or lepton number are not observed experimentally, they are assumed' to play an important role in the early Universe resulting in the existing Baryon Asymmetry of the Universe (BAU). If the asymmetry between matter and antimatter in the early Universe were created by B L conserving interactions (e.g., like in the decay modes of proton p + T O + e+ or p -+ K+ + V ) then BAU would be wiped out at electroweak energy scale by Standard Model interaction^.^ Thus, a new interaction violating B L at energy scale above lo3 GeV is required for an explanation of BAU. Also, heavy Majorana leptons required for the explanation of neutrino masses in the see-saw mechanism4 would violate L and B L numbers by two units. Transitions n + f i could be a natural manifestation of a new physics5 below the Plank scale. Present status and importance of new experimental n 4 f i search are discussed elsewhere.6 With existing experimental facilities the sensitivity of new n 3 f i search experiments can be improved by factor above 1,000. If n 4 A transitions are discovered in future experiments, they can be used as a sensitive test of CPT as was first suggested by Abov, Djeparov, and Okun.' The purpose of this paper is to discuss the sensitivity of new n + f i search experiments to CPT violation effects. Violation of B or B L global numbers is less fundamental than the violation of CPT with the natural scale for the latter to be above the Planck scale. Particle