Protecting the primordial baryon asymmetry in the seesaw model compatible with WMAP and KamLAND

We require that the primordial baryon asymmetry is not washed out in the seesaw model compatible with the recent results of WMAP and the neutrino oscillation experiments including the first results of KamLAND. We find that only the case of the normal neutrino mass hierarchy with an approximate $L_e$ symmetry satisfies this requirement. We further derive, depending on the signs of the neutrino mass eigenvalues, three types of the neutrino mass matrices, where the values of each element are rather precisely fixed.