Radiative Seesaw Model with Baryon Number Violation and Upper Limit on Neutron-anti-Neutron Transition Time

Abstract

The minimal scotogenic model where small neutrino masses arise via radiative seesaw, is known to provide a unified framework for neutrino mass and origin of matter via leptogenesis. However if the inflation reheat temperature of the universe is below the sphaleron reheating temperature, then leptogenesis fails and one way to understand the origin of matter would be to add an effective interaction involving the right handed neutrino (RHN) $N$ of the form $\frac{1}{{\Lambda }^2}N{u}_R{d}_R{d}_R$. This model can lead to observable neutron-anti-neutron ($n-\bar{n}$) oscillation. We show that if RHNs are produced non-thermally, we can get a cosmological upper limit on the transition time ${\tau }_{n-\bar{n}}$, which is within the reach of the planned ESS HIBEAM/NNBAR experiment. The proton stability is guaranteed by the scotogenic $Z_2$ invariance, which prevents the appearance of the Dirac mass term for the neutrino

Comments: 18 pages and 5 figures