Baryogenesis via flavoured leptogenesis in a minimal type-II seesaw model

Abstract

We study baryogenesis via leptogenesis in an extension of the Standard Model by adding one right-handed neutrino and one triplet scalar. These heavy particles contribute to the generation of tiny neutrino mass through seesaw mechanism. The contribution of the heavy particles to the neutrino masses is inversely proportional to their corresponding masses. Considering two cases of mass hierarchy between the right-handed neutrino and triplet scalar, we study baryogenesis via leptogenesis from the decay of either right-handed neutrino or the triplet scalar. The new source of charge conjugation and parity (CP) asymmetry comes from interference of tree-level diagram and one-loop vertex diagram involving the heavy particles. The predictability of the model is enhanced by obtaining a Fritzsch-type texture for the neutrino mass matrix by imposing $A_4\times Z_2$ symmetry. The flavour structure obtained due to the discrete flavour symmetry breaking shows special relation of the CP asymmetry parameter between flavoured and unflavoured leptogenesis. In the two-flavoured regime using the textures we show that there is an enhancement in baryon asymmetry as compared to the unflavoured regime due to the novel washout effects. We also find that the flavour effects in leptogenesis saturate the BAU in the observable range at a mass scale $\sim {10}^{10}$ GeV for triplet leptogenesis, whereas it is $\sim {10}^{11}$ GeV for the right-handed neutrino case. This feature could be attributed to the flavour structure of the model. We also study the common correlation of CP violation between low and high-energy regimes.