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arXiv · 1608.01083

Light dark photon and fermionic dark radiation for the Hubble constant and the structure formation

P. Ko·Yong Tang
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Abstract

Motivated by the tensions in the Hubble constant $H_0$ and the structure growth $σ_8$ between $Planck$ results and other low redshift measurements, we discuss some cosmological effects of a dark sector model in which dark matter (DM) interacts with fermionic dark radiation (DR) through a light gauge boson (dark photon). Such kind of models are very generic in particle physics with a dark sector with dark gauge symmetries. The effective number of neutrinos is increased by $δN_{eff} \sim 0.5$ due to light dark photon and fermionic DR, thereby resolving the conflicts in $H_0$. The elastic scattering between DM and DR induces suppression for DM's density perturbation, but without acoustic oscillations. For weakly-interacting DM around $100$GeV, the new gauge coupling should be $\sim 10^{-4}$ to have sizable effect on matter power spectrum in order to relax the tension in $σ_8$.

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P. Ko, Yong Tang. 2016-10-05. Light dark photon and fermionic dark radiation for the Hubble constant and the structure formation. https://doi.org/10.1016/j.physletb.2016.10.001

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