Holst Ian, Hooper Dan, Krnjaic Gordan
University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois 60637, USA.
University of Chicago, Kavli Institute for Cosmological Physics, Chicago, Illinois 60637, USA.
Phys Rev Lett. 2022 Apr 8;128(14):141802. doi: 10.1103/PhysRevLett.128.141802.
The long-standing 4.2σ muon g-2 anomaly may be the result of a new particle species which could also couple to dark matter and mediate its annihilations in the early Universe. In models where both muons and dark matter carry equal charges under a U(1){L{μ}-L_{τ}} gauge symmetry, the corresponding Z^{'} can both resolve the observed g-2 anomaly and yield an acceptable dark matter relic abundance, relying on annihilations which take place through the Z^{'} resonance. Once the value of (g-2){μ} and the dark matter abundance are each fixed, there is very little remaining freedom in this model, making it highly predictive. We provide a comprehensive analysis of this scenario, identifying a viable range of dark matter masses between approximately 10 and 100 MeV, which falls entirely within the projected sensitivity of several accelerator-based experiments, including NA62, NA64μ, M^{3}, and DUNE. Furthermore, portions of this mass range predict contributions to ΔN{eff} which could ameliorate the tension between early and late time measurements of the Hubble constant, and which could be tested by stage 4 CMB experiments.
长期存在的4.2σμ子g-2反常现象可能是一种新粒子种类的结果，这种新粒子也可能与暗物质耦合，并在早期宇宙中介导其湮灭。在μ子和暗物质在U(1){L{μ}-L_{τ}}规范对称性下携带相等电荷的模型中，相应的Z′既能解决观测到的g-2反常现象，又能产生可接受的暗物质遗迹丰度，这依赖于通过Z′共振发生的湮灭。一旦(g-2){μ}的值和暗物质丰度都确定下来，该模型中剩下的自由度就非常小，使其具有高度的预测性。我们对这种情况进行了全面分析，确定了暗物质质量在大约10到100 MeV之间的可行范围，这完全落在包括NA62、NA64μ、M^{3}和DUNE在内的几个基于加速器的实验的预计灵敏度范围内。此外，这个质量范围的部分预测了对ΔN{eff}的贡献，这可能会缓解哈勃常数早期和晚期测量之间的紧张关系，并且可以通过第4阶段的宇宙微波背景实验进行测试。
