期刊
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
卷 -, 期 7, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2019/07/014
关键词
cosmological neutrinos; neutrino properties; particle physics - cosmology connection; physics of the early universe
资金
- Spanish grants [SEV-2014-0398, FPA2017-85216-P]
- Generalitat Valenciana [PROMETEO/2018/165]
- Red Consolider MultiDark [FPA2017-90566-REDC]
- European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie individual Grant [796941]
- Vetenskapsradet (Swedish Research Council) [638-2013-8993]
- Oskar Klein Centre for Cosmoparticle Physics
- Institute for Theoretical Particle Physics and Cosmology of RWTH Aachen University
- Marie Curie Actions (MSCA) [796941] Funding Source: Marie Curie Actions (MSCA)
In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full 4 x 4 mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, N-eff, and its dependence on the three additional mixing angles (theta(14), theta(24), theta(34)) and on the squared mass difference Delta m(41)(2) is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised (N-eff similar or equal to 4).
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