A Cosmic Window on the Dark Axion Portal

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Hauptverfasser: Hong, Heejoung, Min, Ui, Son, Minho, You, Tevong
Format: Preprint
Veröffentlicht: 2023
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author Hong, Heejoung
Min, Ui
Son, Minho
You, Tevong
author_facet Hong, Heejoung
Min, Ui
Son, Minho
You, Tevong
contents Axions and dark photons are common in many extensions of the Standard Model. The dark axion portal -- an axion coupling to the dark photon and photon -- can significantly modify their phenomenology. We study the cosmological constraints on the dark axion portal from Cosmic Microwave Background (CMB) bounds on the energy density of dark radiation, $ΔN_\text{eff}$. By computing the axion-photon-dark photon collision terms and solving the Boltzmann equations including their effects, we find that light axions are generally more constrained by $ΔN_\text{eff}$ than from supernova cooling or collider experiments. However, with dark photons at the MeV scale, a window of parameter space is opened up above the supernova limits and below the experimental exclusion, allowing for axion decay constants as low as $f_a \sim 10^4$ GeV. This region also modifies indirectly the neutrino energy density, thus relaxing the cosmological upper bound on the sum of neutrino masses. Future CMB measurements could detect a signal or close this open window on the dark axion portal.
format Preprint
id arxiv_https___arxiv_org_abs_2310_19544
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle A Cosmic Window on the Dark Axion Portal
Hong, Heejoung
Min, Ui
Son, Minho
You, Tevong
High Energy Physics - Phenomenology
Axions and dark photons are common in many extensions of the Standard Model. The dark axion portal -- an axion coupling to the dark photon and photon -- can significantly modify their phenomenology. We study the cosmological constraints on the dark axion portal from Cosmic Microwave Background (CMB) bounds on the energy density of dark radiation, $ΔN_\text{eff}$. By computing the axion-photon-dark photon collision terms and solving the Boltzmann equations including their effects, we find that light axions are generally more constrained by $ΔN_\text{eff}$ than from supernova cooling or collider experiments. However, with dark photons at the MeV scale, a window of parameter space is opened up above the supernova limits and below the experimental exclusion, allowing for axion decay constants as low as $f_a \sim 10^4$ GeV. This region also modifies indirectly the neutrino energy density, thus relaxing the cosmological upper bound on the sum of neutrino masses. Future CMB measurements could detect a signal or close this open window on the dark axion portal.
title A Cosmic Window on the Dark Axion Portal
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2310.19544