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| Main Authors: | , , , |
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| Format: | Preprint |
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2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2403.05621 |
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| _version_ | 1866916152802803712 |
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| author | Badziak, Marcin Harigaya, Keisuke Łukawski, Michał Ziegler, Robert |
| author_facet | Badziak, Marcin Harigaya, Keisuke Łukawski, Michał Ziegler, Robert |
| contents | Hot axions are produced in the early Universe via their interactions with Standard Model particles, contributing to dark radiation commonly parameterized as $ΔN_{\text{eff}}$. In standard QCD axion benchmark models, this contribution to $ΔN_{\text{eff}}$ is negligible after taking into account astrophysical limits such as the SN1987A bound. We therefore compute the axion contribution to $ΔN_{\text{eff}}$ in so-called astrophobic axion models characterized by strongly suppressed axion couplings to nucleons and electrons, in which astrophysical constraints are relaxed and $ΔN_{\text{eff}}$ may be sizable. We also construct new astrophobic models in which axion couplings to photons and/or muons are suppressed as well, allowing for axion masses as large as few eV. Most astrophobic models are within the reach of CMB-S4, while some allow for $ΔN_{\text{eff}}$ as large as the current upper bound from Planck and thus will be probed by the Simons Observatory. The majority of astrophobic axion models predicting large $ΔN_{\text{eff}}$ is also within the reach of IAXO or even BabyIAXO. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_05621 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Thermal production of astrophobic axions Badziak, Marcin Harigaya, Keisuke Łukawski, Michał Ziegler, Robert High Energy Physics - Phenomenology Hot axions are produced in the early Universe via their interactions with Standard Model particles, contributing to dark radiation commonly parameterized as $ΔN_{\text{eff}}$. In standard QCD axion benchmark models, this contribution to $ΔN_{\text{eff}}$ is negligible after taking into account astrophysical limits such as the SN1987A bound. We therefore compute the axion contribution to $ΔN_{\text{eff}}$ in so-called astrophobic axion models characterized by strongly suppressed axion couplings to nucleons and electrons, in which astrophysical constraints are relaxed and $ΔN_{\text{eff}}$ may be sizable. We also construct new astrophobic models in which axion couplings to photons and/or muons are suppressed as well, allowing for axion masses as large as few eV. Most astrophobic models are within the reach of CMB-S4, while some allow for $ΔN_{\text{eff}}$ as large as the current upper bound from Planck and thus will be probed by the Simons Observatory. The majority of astrophobic axion models predicting large $ΔN_{\text{eff}}$ is also within the reach of IAXO or even BabyIAXO. |
| title | Thermal production of astrophobic axions |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2403.05621 |