论文标题
$ u（1）$标准模型的扩展
Axion and FIMP Dark Matter in a $U(1)$ extension of the Standard Model
论文作者
论文摘要
在标准模型中，缺少暗物质的候选者，但是扩大包括一个或多个合适粒子的模型相对简单。我们在本文中考虑了这种扩展，灵感来自简单性和目标，而不仅仅是解决暗物质问题。实际上，我们考虑了SM的局部$ U（1）$扩展，该扩展提供了一个轴粒子来解决强大的CP问题，并包括具有适当质量项的RH Neutrinos。后者之一与Sm瘦素分离，可以构成稳定的无菌中微子DM。在这种情况下，PQ对称性仅作为意外对称性产生，但它被高阶操作员的破裂足够抑制，以避免引入大型$θ$贡献。轴衰变常数和RH中微子质量与相同的V.E.V.S和PQ量表有关，并且两个DM密度都取决于轴和标量扇形的参数。该模型通常预测具有轴和无菌中微子DM的混合暗物质情景，其特征是每个组件的密度和观察信号降低。
In the Standard Model a Dark Matter candidate is missing, but it is relatively simple to enlarge the model including one or more suitable particles. We consider in this paper one such extension, inspired by simplicity and by the goal to solve more than just the Dark Matter issue. Indeed we consider a local $U(1) $ extension of the SM providing an axion particle to solve the strong CP problem and including RH neutrinos with appropriate mass terms. One of the latter is decoupled from the SM leptons and can constitute stable sterile neutrino DM. In this setting, the PQ symmetry arises only as an accidental symmetry but its breaking by higher order operators is sufficiently suppressed to avoid introducing a large $ θ$ contribution. The axion decay constant and the RH neutrino masses are related to the same v.e.v.s and the PQ scale and both DM densities are determined by the parameters of the axion and scalar sector. The model predicts in general a mixed Dark Matter scenario with both axion and sterile neutrino DM and is characterised by a reduced density and observational signals from each single component.
