SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Fermi National Accelerator Laboratory, Theoretical Astrophysics Group, Batavia, Illinois 60510, USA.
Phys Rev Lett. 2018 Jul 6;121(1):011102. doi: 10.1103/PhysRevLett.121.011102.
The EDGES Collaboration has recently reported the detection of a stronger-than-expected absorption feature in the global 21-cm spectrum, centered at a frequency corresponding to a redshift of z≃17. This observation has been interpreted as evidence that the gas was cooled during this era as a result of scattering with dark matter. In this Letter, we explore this possibility, applying constraints from the cosmic microwave background, light element abundances, Supernova 1987A, and a variety of laboratory experiments. After taking these constraints into account, we find that the vast majority of the parameter space capable of generating the observed 21-cm signal is ruled out. The only viable models are those in which a small fraction, ∼0.3%-2%, of the dark matter consists of particles with a mass of ∼10-80 MeV and which couple to the photon through a small electric charge, roughly 10^{-6}-10^{-4} as large as the electron charge. Furthermore, in order to avoid being overproduced in the early Universe, such models must be supplemented with an additional depletion mechanism, such as annihilations through a L_{μ}-L_{τ} gauge boson or annihilations to a pair of rapidly decaying hidden sector scalars.
EDGES 合作最近报告称，在全球 21 厘米光谱中检测到一个比预期更强的吸收特征，其中心频率对应红移 z≃17。这一观测结果被解释为证据，表明在这个时代，由于与暗物质的散射，气体被冷却了。在这封信中，我们探讨了这种可能性，应用了宇宙微波背景、轻元素丰度、超新星 1987A 和各种实验室实验的限制。在考虑了这些限制之后，我们发现，能够产生观测到的 21 厘米信号的绝大多数参数空间都被排除了。唯一可行的模型是那些只有一小部分（约 0.3%-2%）暗物质由质量约为 10-80 MeV 的粒子组成，并且通过一个小电荷与光子耦合，大约是电子电荷的 10^{-6}-10^{-4}。此外，为了避免在早期宇宙中过度产生，这种模型必须补充额外的耗尽机制，例如通过 L_{μ}-L_{τ}规范玻色子或湮灭到一对快速衰变的隐藏领域标量来湮灭。
