标题： 规范$L_e-L_μ-L_τ$对称性，第四代，中微子质量与暗物质 显示英文标题

标题： Gauged $L_e-L_μ-L_τ$ symmetry, fourth generation, neutrino mass and dark matter

摘要： 我们提出两种模型，在这些模型中熟悉的轻子对称性$L_e-L_\mu-L_\tau$是一种规范对称性。 我们展示了反常抵消如何限制允许的理论，其中一种模型需要第四代顺序手征标准模型费米子生成，另一种模型有三代，需要对$(L_e-L_\mu-L_\tau)-(B_1-B_2-B_3)$进行规范，并且$B_a$表示$a$代夸克的重子数。 与总是导致中微子倒质量层次的全局$L_e-L_\mu-L_\tau$模型不同，规范版本可能导致正常质量层次。 我们展示了如何在这两种情况下构建现实模型，并讨论了这两种情况下的暗物质候选者。 在我们的模型中，$U(1)_{L_e-L_\mu-L_\tau}$的破坏通过类型-I机制导致中微子质量，而$U(1)_{L_e-L_\mu-L_\tau}$破坏标量场的实部（在此称为$\phi$）起到冻结注入暗物质候选者的作用。 由于$\phi$不稳定，为了成为暗物质，其寿命必须大于宇宙的年龄，这意味着$\phi$的残留物是通过冻结注入机制产生的，且其质量必须小于一个MeV。 我们还讨论了同时解释缪子和电子$(g-2)$的可能性，同时满足暗物质残留密度和寿命约束。 显示英文摘要

摘要： We present two models where the familiar leptonic symmetry $L_e-L_\mu-L_\tau$ is a gauge symmetry. We show how anomaly cancellation constrains the allowed theories, with one of them requiring a fourth sequential chiral standard model fermion generation and a second one with three generations, requiring gauging of $(L_e-L_\mu-L_\tau)-(B_1-B_2-B_3)$ with $B_a$ representing the baryon number of the $a$th generation quarks. Unlike global $L_e-L_\mu-L_\tau$ models which always leads to inverted mass hierarchy for neutrinos, the gauged version can lead to normal hierarchy. We show how to construct realistic models in both the cases and discuss the dark matter candidate in both. In our model, the breaking of $U(1)_{L_e-L_\mu-L_\tau}$ is responsible for neutrino mass via type-I mechanism whereas the real part of $U(1)_{L_e-L_\mu-L_\tau}$ breaking scalar field (called $\phi$ here) plays the role of freeze-in dark matter candidate. Since $\phi$ is unstable, for it to qualify as dark matter, its lifetime must be larger than the age of the Universe, implying that the relic of $\phi$ is generated through freeze-in mechanism and its mass must be less than an MeV. We also discuss the possibility of explaining both muon and electron $(g-2)$ while being consistent with the dark matter relic density and lifetime constraints.