Leptogenesis Constraints on the Mass of Right-handed Gauge Bosons

Abstract

We discuss leptogenesis constraints on the mass of the right-handed $W$-boson ($W_R$) in a TeV-scale Left-Right seesaw model (LRSM) for neutrino masses. For generic Dirac mass of the neutrinos, i.e. with all Yukawa couplings $\lesssim 10^{-5.5}$, it has been pointed out that successful leptogenesis requires a lower bound of 18 TeV on the $W_R$ mass, pushing it beyond the reach of LHC. Such TeV-scale LRSM must, however, be parity-asymmetric for type-I seesaw to give the observed neutrino masses. This class of models can accommodate larger Yukawa couplings, which give simultaneous fits to charged-lepton and neutrino masses, by invoking either cancellations or specific symmetry-textures for Dirac ($M_D$) and Majorana ($M_N$) masses in the seesaw formula. We show that in this case, the leptogenesis bound on $M_{W_R}$ can be substantially weaker, i.e. $M_{W_R}\gtrsim 3$ TeV for $M_N\lesssim M_{W_R}$. This happens due to considerable reduction of the dilution effects from $W_R$-mediated decays and scatterings, while the washout effects due to inverse decays are under control for certain parameter ranges of the Yukawa couplings. We also show that this model is consistent with all other low energy constraints, such as lepton flavor violation and neutrinoless double beta decay. Thus, a discovery of the right-handed gauge bosons alone at the LHC will not falsify leptogenesis as the mechanism behind the matter-antimatter asymmetry in our Universe.

29 pages, 5 figures, 2 tables; some clarifications and references added; version accepted for publication in Phys. Rev. D

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• TeV Scale Left-Right Symmetry and Large Mixing Effects in Neutrinoless Double Beta Decay
• Double Beta Decay, Lepton Flavour Violation and Collider Signatures of Left-Right Symmetric Models with Spontaneous D Parity Breaking
• Explanation of the 95 GeV $\gamma \gamma$ and $b\bar{b}$ excesses in the Minimal Left-Right Symmetric Model
• Neutrinoless Double Beta Decay in LRSM with Natural Type-II seesaw Dominance
• Lepton Number Violation, Lepton Flavour Violation and Baryogenesis in Left-Right Symmetric Model
• Neutrino Mass and Neutrinoless double beta decay in SO(10) GUT with Pati-Salam symmetry
• $A_4$ realization of left-right symmetric linear seesaw
• Impact of Lepton Number Violation at the LHC on Models of Leptogenesis
• Neutrino mass and charged lepton flavor violation in an extended left-right symmetric model