Primordial Lepton Family Asymmetries in Seesaw Model

Abstract

In the leptogenesis scenario, decays of heavy Majorana neutrinos generate lepton family asymmetries, Ye, Yμ and Yτ. These asymmetries are sensitive to CP violating phases in seesaw models. The time evolution of the lepton family asymmetries is derived by solving Boltzmann equations. Considering a minimal seesaw model, we show how each family asymmetry varies with one particular CP violating phase. for instance, we find the case in which the lepton asymmetry is dominated by Yμ or Yτ, depending on the choice of the CP violating phase. We also find the case in which the signs of the lepton family asymmetries Yμ and Yτ are opposite. Their absolute values can be larger than the total lepton asymmetry, and baryon asymmetry may result from the cancellation of the lepton family asymmetries.