Thermal axion production at hard and soft momenta
Abstract Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from N eff. In this paper we quantify the contribution to N eff and its uncertainty in models with axion-gluon couplings from thermal dynamics abov...
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| Format: | Article |
| Language: | English |
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2025-01-01
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| Series: | Journal of High Energy Physics |
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| Online Access: | https://doi.org/10.1007/JHEP01(2025)163 |
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| author | Killian Bouzoud Jacopo Ghiglieri |
| author_facet | Killian Bouzoud Jacopo Ghiglieri |
| author_sort | Killian Bouzoud |
| collection | DOAJ |
| description | Abstract Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from N eff. In this paper we quantify the contribution to N eff and its uncertainty in models with axion-gluon couplings from thermal dynamics above the QCD transition. In more detail, we determine the leading-order thermal axion production rate for axion momenta of the order of the temperature adopting three different schemes for the incorporation of the collective dynamics of soft gluons. We show how these three schemes extrapolate differently into the regime of softer axion production, thus giving us a first quantitative handle on the theory uncertainty of the rate. Upon solving the Boltzmann equation, we find that this theory uncertainty translates to an uncertainty of order 0.002 for the contribution to N eff prior to the QCD crossover. The uncertainty from common momentum-averaged approximations to the Boltzmann equation is smaller. We also discuss how QCD transition dynamics would need to be integrated into our results and we show how existing rate determinations in the literature based on gauge-dependent resummations are problematic. |
| format | Article |
| id | doaj-art-46ba7976cf144eaa873e1427f44833d3 |
| institution | Kabale University |
| issn | 1029-8479 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj-art-46ba7976cf144eaa873e1427f44833d32025-02-09T12:08:11ZengSpringerOpenJournal of High Energy Physics1029-84792025-01-012025114410.1007/JHEP01(2025)163Thermal axion production at hard and soft momentaKillian Bouzoud0Jacopo Ghiglieri1SUBATECH, Nantes Université, IMT Atlantique, IN2P3/CNRSSUBATECH, Nantes Université, IMT Atlantique, IN2P3/CNRSAbstract Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from N eff. In this paper we quantify the contribution to N eff and its uncertainty in models with axion-gluon couplings from thermal dynamics above the QCD transition. In more detail, we determine the leading-order thermal axion production rate for axion momenta of the order of the temperature adopting three different schemes for the incorporation of the collective dynamics of soft gluons. We show how these three schemes extrapolate differently into the regime of softer axion production, thus giving us a first quantitative handle on the theory uncertainty of the rate. Upon solving the Boltzmann equation, we find that this theory uncertainty translates to an uncertainty of order 0.002 for the contribution to N eff prior to the QCD crossover. The uncertainty from common momentum-averaged approximations to the Boltzmann equation is smaller. We also discuss how QCD transition dynamics would need to be integrated into our results and we show how existing rate determinations in the literature based on gauge-dependent resummations are problematic.https://doi.org/10.1007/JHEP01(2025)163Axions and ALPsCosmology of Theories BSMEarly Universe Particle PhysicsThermal Field Theory |
| spellingShingle | Killian Bouzoud Jacopo Ghiglieri Thermal axion production at hard and soft momenta Journal of High Energy Physics Axions and ALPs Cosmology of Theories BSM Early Universe Particle Physics Thermal Field Theory |
| title | Thermal axion production at hard and soft momenta |
| title_full | Thermal axion production at hard and soft momenta |
| title_fullStr | Thermal axion production at hard and soft momenta |
| title_full_unstemmed | Thermal axion production at hard and soft momenta |
| title_short | Thermal axion production at hard and soft momenta |
| title_sort | thermal axion production at hard and soft momenta |
| topic | Axions and ALPs Cosmology of Theories BSM Early Universe Particle Physics Thermal Field Theory |
| url | https://doi.org/10.1007/JHEP01(2025)163 |
| work_keys_str_mv | AT killianbouzoud thermalaxionproductionathardandsoftmomenta AT jacopoghiglieri thermalaxionproductionathardandsoftmomenta |