Reheating-temperature independence of cosmological baryon asymmetry in Affleck-Dine leptogenesis

Abstract

In this paper we point out that the cosmological baryon asymmetry in our universe is generated almost independently of the reheating temperature ${T}_{R}$ in Affleck-Dine leptogenesis and it is determined mainly by the mass of the lightest neutrino, ${m}_{{\ensuremath{\nu}}_{1}},$ in a wide range of reheating temperature ${T}_{R}\ensuremath{\simeq}{10}^{5}--{10}^{12}\mathrm{GeV}.$ The present baryon asymmetry predicts the ${m}_{{\ensuremath{\nu}}_{1}}$ in a narrow region ${m}_{{\ensuremath{\nu}}_{1}}\ensuremath{\simeq}(0.1--3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\mathrm{eV}.$ Such a small mass of the lightest neutrino leads to a high predictability on the mass parameter ${m}_{{\ensuremath{\nu}}_{e}{\ensuremath{\nu}}_{e}}$ contributing to the neutrinoless double beta decay. We also propose an explicit model in which such an ultralight neutrino can be naturally obtained.