Neutrino magnetic moments meet precision N eff measurements

Abstract In the early universe, Dirac neutrino magnetic moments due to their chirality-flipping nature could lead to thermal production of right-handed neutrinos, which would make a significant contribution to the effective neutrino number, N eff. We present in this paper a dedicated computation of...

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Published inThe journal of high energy physics Vol. 2023; no. 2; pp. 1 - 27
Main Authors Shao-Ping Li, Xun-Jie Xu
Format Journal Article
LanguageEnglish
Published SpringerOpen 01.02.2023
Subjects
Cosmology of Theories BSM
Early Universe Particle Physics
Neutrino Interactions
Non-Standard Neutrino Properties
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Summary:Abstract In the early universe, Dirac neutrino magnetic moments due to their chirality-flipping nature could lead to thermal production of right-handed neutrinos, which would make a significant contribution to the effective neutrino number, N eff. We present in this paper a dedicated computation of the neutrino chirality-flipping rate in the thermal plasma. With a careful and consistent treatment of soft scattering and the plasmon effect in finite temperature field theories, we find that neutrino magnetic moments above 2.7 × 10 −12 μ B have been excluded by current CMB and BBN measurements of N eff, assuming flavor-universal and diagonal magnetic moments for all three generation of neutrinos. This limit is stronger than the latest bounds from XENONnT and LUX-ZEPLIN experiments and comparable with those from stellar cooling considerations.
ISSN:1029-8479
DOI:10.1007/JHEP02(2023)085