We propose a hybrid seesaw model based on $A_{4}$ flavor symmetry, which generates a large hierarchical flavor structure. In our model, tree-level and one-loop seesaw mechanisms predict different flavor structures in the neutrino mass matrix and generate a notable hierarchy among them. We find that such a hierarchical structure gives a large effective neutrino mass that can be accessible by next-generation neutrinoless double beta decay experiments. Majorana phases can also be predictable. The $A_{4}$ flavor symmetry in the model is spontaneously broken to the $Z_{2}$ symmetry, leading to a dark matter candidate that is assumed to be a neutral scalar field. The favored mass region of the dark matter is obtained by numerical computations of the relic abundance and the cross section of the nucleon. We also investigate the predictions of several hierarchical flavor structures based on $A_{4}$ symmetry for the effective neutrino mass and the Majorana phases, and find characteristic features depending on the hierarchical structures.

中文翻译：

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基于A4对称的混合跷跷板模型和分层中微子风味结构

我们提出了一种基于 $A_{4}$ 风味对称性的混合跷跷板模型，它生成了一个大的层次风味结构。在我们的模型中，树级和单环跷跷板机制预测中微子质量矩阵中的不同风味结构，并在它们之间产生显着的层次结构。我们发现这种分层结构提供了一个大的有效中微子质量，可以通过下一代无中微子双β衰变实验获得。马约拉纳阶段也可以预测。模型中的 $A_{4}$ 风味对称性自发地破坏为 $Z_{2}$ 对称性，导致暗物质候选者被假定为中性标量场。暗物质的有利质量区域是通过对残骸丰度和核子截面的数值计算得出的。