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Axion Dark Radiation: Hubble Tension and Hyper-kamiokande Neutrino Experiment by Gu, Yuchao; Wu, Lei; Zhu, Bin is a scholarly article available to read on EtoBox.

What is Axion Dark Radiation: Hubble Tension and Hyper-kamiokande Neutrino Experiment about?

In this work, we investigate the dark sector of a supersymmetric axion model, consisting of the late-decaying gravitino/axino dark matter and axion dark radiation. In the early universe, the decay of the scalar superpartner of the axion (saxion) will produce a large amount of entropy. The additional entropy can not only dilute the relic density of the gravitino/axino dark matter to avoid overclosing the universe but also relax the constraint on the reheating temperature $T_{R}$ after inflation. Meanwhile, the axion dark radiation from the saxion decay will increase the effective number of neutrino species $N_{\rm eff}$, which can help to reduce the cosmological Hubble tension. In the late universe, the decay of long-lived gravitino/axino dark matter produces the axions with MeV-scale kinetic energy. We study the potential of searching for such energetic axions through the inverse Primakoff process $a+A \to \gamma+ A$ in the neutrino experiments, such as Hyper-Kamiokande.

Author

Gu, Yuchao; Wu, Lei; Zhu, Bin

Published

2021

Language

EN