Abstract
We propose a two-component dark matter explanation to the EDGES 21 cm anomalous signal. The heavier dark matter component is long-lived, and its decay is primarily responsible for the relic abundance of the lighter dark matter, which is millicharged. To evade the constraints from CMB, underground dark matter direct detection, and XQC experiments, the lifetime of the heavier dark matter has to be larger than , where is the age of the universe. Our model provides a viable realization of the millicharged dark matter model to explain the EDGES 21 cm signal, since the minimal model in which the relic density is generated via thermal freeze-out has been ruled out by various constraints.
Highlights
We propose a two-component dark matter explanation to the EDGES 21 cm anomalous signal
Ref. [22] proposed a new millicharged DM model in which the sub-component millicharged DM has a sizable interaction cross section with the other DM components so that the millicharged DM can be cooled by the other DM components; this reopens the parameter space that was previously excluded by various experimental constraints
We show that such a model can explain the 21 cm anomaly observed by EDGES and satisfy various experimental constraints
Summary
We extend the standard model (SM) by introducing a hidden sector that consists of three. The mass matrix of the first two gauge bosons (the upper-left two by two block matrix in Eq (2.2)) can be diagonalized via a rotation matrix R which is parameterized by a single angle θ cos θ − sin θ. M32×3 is the bottom-right three by three block matrix in Eq (2.2) Such a matrix diagonalization leads to interactions between matter fields (both hidden sector fermion χ and SM fermions f ) and the three mass eigenstates (γ, Z, and Z ). We adopt the following model parameters: m3 = 100 TeV, and m4/m3 1 In this case, the electric charge is given by. 1, which is often referred to as millicharge. χ is the millicharged particle
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