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

TL;DR

This paper explores a radiative seesaw model with baryon number violation that predicts observable neutron-antineutron oscillations and establishes an upper limit on the transition time, linking cosmology and experimental prospects.

Contribution

It introduces a variant of the scotogenic model with baryon number violation, deriving a cosmological upper limit on neutron-antineutron transition time within experimental reach.

Findings

Neutron-antineutron oscillation transition time is within planned experimental sensitivity.

Non-thermal production of right-handed neutrinos constrains the transition time.

Proton stability is maintained by a Z2 symmetry in the model.

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 $\frac{1}{\Lambda^2}N u_Rd_Rd_R$. 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