Flavor symmetries, leptogenesis and the absolute neutrino mass scale

Abstract

We study the interplay between flavor symmetries and leptogenesis in the case when the scale of flavor symmetry breaking is higher than the scale at which lepton number is violated. We show that when the heavy Majorana neutrinos belong to an irreducible representation of the flavor group, all the leptogenesis CP asymmetries vanish in the limit of exact symmetry. In the case of reducible representations we identify a general condition that, if satisfied, guarantees the same result. We then focus on the case of a model in which an $A_4$ flavor symmetry yields a drastic reduction in the number of free parameters, implying that at leading order several quantities are only a function of the lightest neutrino mass $m_l$, which in turn is strongly constrained. For normal ordering (NO) we find m_l\simeq (0.0044 ÷0.0056) eV while for inverted ordering (IO) m_l\gtrsim 0.017 eV. For the 0\nu2βdecay parameter this yields |m_{ee}|\simeq (0.006÷0.007) eV (NO) and |m_{ee}|\gsim 0.017 eV (IO). We show that the leptogenesis CP asymmetries only depend on m_l, on a single non-hierarchical Yukawa coupling y, and on two parameters that quantify the flavor symmetry breaking effects, and we argue that the unflavored regime for leptogenesis is strongly preferred in our model, thus realizing a rather predictive scenario. Performing a calculation of the matter-antimatter asymmetry we find that for NO the observed value is easily reproduced for natural values of the symmetry breaking parameters. For IO successful leptogenesis is possible for a limited choice of the parameters implying rather large reheating temperatures T_reh\gtrsim 5*10^13 GeV.

38 pages, 7 figures; v2: References added, typos corrected, 1 acknowledgement added, Eq. (69) replaces Eq. (68) in v1 with consequent changes in figures 4-7. All conclusions unchanged

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• Particle Physics at the European Spallation Source
• Adjoint SUSY $SU(5)$ Grand Unified Model with $S_4$ Flavor Symmetry
• On the origin of matter in the Universe
• Dynamical Minimal Flavour Violating Inverse Seesaw
• Leptonic mixing, family symmetries, and neutrino phenomenology
• Vacuum misalignment corrections to tri-bimaximal mixing and form dominance
• Reactor mixing angle from hybrid neutrino masses
• Baryon asymmetry via leptogenesis in a neutrino mass model with complex scaling
• Generalized ${\mathbb{Z}}_2\times {\mathbb{Z}}_2$ in Scaling neutrino Majorana mass matrix and baryogenesis via flavored leptogenesis
• Baryon asymmetry and lower bound on right handed neutrino mass in fast expanding Universe: an analytical approach
• Probing flavored regimes of leptogenesis with gravitational waves from cosmic strings
• Baryogenesis via leptogenesis from quark-lepton symmetry\par and a compact heavy $N_R$ spectrum
• Low-scale leptogenesis with flavour and CP symmetries
• The Dark Side of ${\theta }_{13}$, ${\delta }_{CP}$, Leptogenesis and Inflation in Type-I Seesaw