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arXiv 1910.04467hep-ph
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$μ-τ$对称性破缺的幻中微子质量模型与轻子生成

Magic neutrino mass model with broken $μ-τ$ symmetry and Leptogenesis

Surender Verma, Monal Kashav

摘要:

研究了在$A_4$味模型中,在两个右手中微子(2RHN)的最小情形下,在I型和II型跷跷板机制的范式下,通过瘦生作用产生重子,得到$μ-τ$对称性破缺的幻数中微子质量矩阵.通过引入额外的$Z_3$循环对称性来约束模型的Yukawa结构。第二类跷跷板项在产生非简并中微子质量和非零$θ_{13}$中起着至关重要的作用,并对重子生成有贡献。特别地,在自发对称性破缺之后,Yukawa耦合$y_{Δ_1}$和$y_{Δ_3}$负责$μ-τ$对称性的破缺。有效的Majorana中微子质量$|M_{ee}|$被发现是在$0νββ$实验的灵敏度范围内,特别是,对倒置的层次。该模型对倒置层次结构具有重要意义,例如,在nEXO中未观察到该过程将排除IH。预测的重子不对称性与观察到的NH重子不对称性很好地一致,而IH在2.5 $σ$ C. L.是不允许的。

英文摘要:

We investigate baryogenesis via leptogenesis in $A_4$ flavor model within the paradigm of type-I and II seesaw mechanism resulting in magic neutrino mass matrix with broken $μ-τ$ symmetry in a minimal scenario with two right-handed neutrinos(2RHN). Additional $Z_3$ cyclic symmetry is employed to constrain the Yukawa structure of model. The type-II seesaw terms play crucial role in generating non-degenerate neutrino masses and non-zero $θ_{13}$ and contribute in baryogenesis. In particular, after the spontaneous symmetry breaking, the Yukawa couplings $y_{Δ_1}$ and $y_{Δ_3}$ are responsible for the breaking of $μ-τ$ symmetry. The effective Majorana neutrino mass $|M_{ee}|$ is found to be well within the sensitivity reach of the $0νββ$ experiments, in particular, for inverted hierarchy. The model has imperative implication for inverted hierarchy, for example, the non-observation of this process at nEXO will rule out IH. The predicted baryon asymmetry is in good agreement with the observed baryon asymmetry for NH whereas IH is disallowed at 2.5$σ$ C.L..

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