Primordial Lepton Family Asymmtries in Seesaw Model

Abstract

In leptogenesis scenario, the decays of heavy Majorana neutrinos generate lepton family asymmetries, \(Y_e, Y_{\mu}\) and \(Y_{\tau}\). They are sensitive to CP violating phases in seesaw models. The time evolution of the lepton family asymmetries are derived by solving Boltzmann equations. By taking a minimal seesaw model, we show how each family asymmetry varies with a CP violating phase. For instance, we find the case that 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 that the signs of lepton family asymmetries \(Y_{\mu}\) and \(Y_{\tau}\) are opposite each other. Their absolute values can be larger than the total lepton asymmetry and the baryon asymmetry may result from the cancellation of the lepton family asymmetries.