Primordial lepton family asymmetries in seesaw model

In the leptogenesis scenario, decays of heavy Majorana neutrinos generate lepton family asymmetries, Y-e, Y-mu and Y-tau. 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 Y-mu or Y-tau, depending on the choice of the CP violating phase. We also find the case in which the signs of the lepton family asymmetries Y-mu and Y-tau 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.