Enabling Strong Neutrino Self-interaction with an Unparticle Mediator
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| author | Foroughi-Abari, Saeid Kelly, Kevin J. Rai, Mudit Zhang, Yue |
| author_facet | Foroughi-Abari, Saeid Kelly, Kevin J. Rai, Mudit Zhang, Yue |
| contents | Recent explorations of the cosmic microwave background and the large-scale structure of the universe have indicated a preference for sizable neutrino self-interactions, much stronger than what the Standard Model offers. When interpreted in the context of simple particle-physics models with a light, neutrinophilic scalar mediator, some of the hints are already in tension with the combination of terrestrial, astrophysical and cosmological constraints. We take a novel approach by considering neutrino self-interactions through a mediator with a smooth, continuous, spectral density function. We consider Georgi's unparticle with a mass gap as a concrete example and point out two useful effects for mitigating two leading constraints. 1) The Unparticle is ``broadband'' -- it occupies a wide range of masses which allows it to pass the early universe constraint on effective number of extra neutrinos ($ΔN_{\rm eff.}$) even if the mass gap lies below the MeV scale. 2) Scattering involving unparticles is less resonant -- which lifts the constraint set by IceCube based on a recent measurement of ultra-high-energy cosmogenic neutrinos. Our analysis shows that an unparticle mediator can open up ample parameter space for strong neutrino self-interactions of interest to cosmology and serves a well-motivated target for upcoming experiments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_02049 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Enabling Strong Neutrino Self-interaction with an Unparticle Mediator Foroughi-Abari, Saeid Kelly, Kevin J. Rai, Mudit Zhang, Yue High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena High Energy Physics - Experiment Recent explorations of the cosmic microwave background and the large-scale structure of the universe have indicated a preference for sizable neutrino self-interactions, much stronger than what the Standard Model offers. When interpreted in the context of simple particle-physics models with a light, neutrinophilic scalar mediator, some of the hints are already in tension with the combination of terrestrial, astrophysical and cosmological constraints. We take a novel approach by considering neutrino self-interactions through a mediator with a smooth, continuous, spectral density function. We consider Georgi's unparticle with a mass gap as a concrete example and point out two useful effects for mitigating two leading constraints. 1) The Unparticle is ``broadband'' -- it occupies a wide range of masses which allows it to pass the early universe constraint on effective number of extra neutrinos ($ΔN_{\rm eff.}$) even if the mass gap lies below the MeV scale. 2) Scattering involving unparticles is less resonant -- which lifts the constraint set by IceCube based on a recent measurement of ultra-high-energy cosmogenic neutrinos. Our analysis shows that an unparticle mediator can open up ample parameter space for strong neutrino self-interactions of interest to cosmology and serves a well-motivated target for upcoming experiments. |
| title | Enabling Strong Neutrino Self-interaction with an Unparticle Mediator |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics High Energy Astrophysical Phenomena High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2501.02049 |