Deppisch, Frank F;
Gonzalo, Tomas E;
Majumdar, Chayan;
Zhang, Zhong;
(2025)
Relaxing limits from Big Bang Nucleosynthesis on Heavy Neutral Leptons with axion-like particles.
Journal of Cosmology and Astroparticle Physics
, 2025
(2)
, Article 054. 10.1088/1475-7516/2025/02/054.
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Abstract
Heavy neutral leptons (HNLs) are constrained by requirements of Big Bang Nucleosynthesis (BBN) as their decays significantly impact the formation of the primordial elements. We propose here a model where the primary decay channel for the HNLs is to an axion-like particle (ALP) and a neutrino. Consequently, HNLs can decay earlier and evade the BBN bound for lower masses, provided the ALPs themselves decay considerably later. Further cosmological and astrophysical constraints limit severely the range of validity of the ALP properties. We find that a new parameter region opens up for HNLs with masses between 1 MeV and 1 GeV, and active-sterile neutrino mixing strengths between 10<sup>-9</sup> and 10<sup>-6</sup> that is consistent with constraints and can be probed in future searches. In such a scenario, current bounds as well as sensitivities of future direct HNL searches such as at NA62 and DUNE will be affected.
| Type: | Article |
|---|---|
| Title: | Relaxing limits from Big Bang Nucleosynthesis on Heavy Neutral Leptons with axion-like particles |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1088/1475-7516/2025/02/054 |
| Publisher version: | https://doi.org/10.1088/1475-7516/2025/02/054 |
| Language: | English |
| Additional information: | © 2025 The Author(s). Published by IOP Publishing Ltd on behalf of Sissa Medialab. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence (http://creativecommons.org/licenses/by/4.0). |
| Keywords: | axions, big bang nucleosynthesis, neutrino experiments, particle physics - cosmology connection |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10216908 |
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