Abstract:

A new experiment to search for neutron-to-antineutron transitions (NNbar) in vacuum is proposed for the Deep Underground Science and Engineering Laboratory. The motivation for this search was greatly enhanced by the recent discovery of the neutrino masses, requiring for its explanation a seesaw mechanism with the heavy Majorana particle. The same mechanism leads to NNbar transitions. It was recently realized that "standard" proton decay is not a prediction of baryogenisis. Baryogenesis and Leptogenesis require non-conservation of B-L; a search for neutron to antineutron transitions in vacuum provides the highest sensitivity for the observation of new physics with B-L non-conservation. In the proposed experiment, a 1-km vertical shaft at the DUSEL site with a TRIGA reactor at the top and an antineutron annihilation detector at the bottom of the shaft can deliver a sensitivity to Nnbar transitions a factor of 1,000-10,000 above the present limits.