Lepton asymettry in $S_3$ extended Standard Model

Abstract

Standard model (SM) of electroweak interaction seems to be complete and consistent with almost all the data obtained so far, nevertheless, some deviations in the B sector are observed apart from the neutrino oscillation. It is believed that the SM is not a complete theory as we cannot explain the matter-antimatter asymmetry in our Universe in addition to the fact that the visible Universe contains just 5% of the total energy budget. We consider leptogenesis in a minimal S 3 extended standard model with a Higgs doublet and 3 right handed singlet Majorana neutrinos. We studied the neutrino phenomenology from the flavor structure of the S 3 invariant mass matrix in compatible with the 1σ experimental oscillation parameters.We have chosen the out of equilibrium decays of the lightest right handed Majorana neutrino to be in the temeperature range less than 10 8 GeV, where one flavor approximation isn't valid as all the charged lepton yukawa couplings are in equilibrium. Hence we can distinguish between the τ and other lepton flavors. Thereafter, we generate the lepton asymmetry by adding flavor effects coming individually from all the leptons sector. This flavor approximation can generate an appreciable lepton asymmetry which can convert to the baryon asymmetry through sphaleron process and can account for the experimental observation. Imposition of S 3 flavor structure of the yukawa couplings restrict the asymmetry in the τ sector to vanish whereas the asymmetries in other leptons sector remain finite.