Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Kavli Institute for Cosmology, Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom.
Phys Rev Lett. 2015 Aug 14;115(7):071304. doi: 10.1103/PhysRevLett.115.071304.
We propose a new method to constrain elastic scattering between dark matter (DM) and standard model particles in the early Universe. Direct or indirect thermal coupling of nonrelativistic DM with photons leads to a heat sink for the latter. This results in spectral distortions of the cosmic microwave background (CMB), the amplitude of which can be as large as a few times the DM-to-photon-number ratio. We compute CMB spectral distortions due to DM-proton, DM-electron, and DM-photon scattering for generic energy-dependent cross sections and DM mass m_{χ}≳1 keV. Using Far-Infrared Absolute Spectrophotometer measurements, we set constraints on the cross sections for m_{χ}≲0.1 MeV. In particular, for energy-independent scattering we obtain σ_{DM-proton}≲10^{-24} cm^{2} (keV/m_{χ})^{1/2}, σ_{DM-electron}≲10^{-27} cm^{2} (keV/m_{χ})^{1/2}, and σ_{DM-photon}≲10^{-39} cm^{2} (m_{χ}/keV). An experiment with the characteristics of the Primordial Inflation Explorer would extend the regime of sensitivity up to masses m_{χ}~1 GeV.
我们提出了一种新方法来约束早期宇宙中暗物质 (DM) 和标准模型粒子之间的弹性散射。非相对论性 DM 与光子的直接或间接热耦合会导致后者的热汇。这会导致宇宙微波背景 (CMB) 的光谱扭曲，其幅度可以达到 DM-光子数比的几倍。我们针对一般的能量相关散射截面和 DM 质量 m_{χ}≳1 keV 计算了 DM-质子、DM-电子和 DM-光子散射引起的 CMB 光谱扭曲。利用远红外绝对分光光度计测量，我们对 m_{χ}≲0.1 MeV 时的截面施加了限制。特别是对于能量无关的散射，我们得到 σ_{DM-proton}≲10^{-24} cm^{2} (keV/m_{χ})^{1/2}、σ_{DM-electron}≲10^{-27} cm^{2} (keV/m_{χ})^{1/2} 和 σ_{DM-photon}≲10^{-39} cm^{2} (m_{χ}/keV)。具有原始通货膨胀探测器特征的实验将把灵敏度扩展到质量 m_{χ}~1 GeV。
