Sterile neutrinos with eV masses in cosmology — How disfavoured exactly?

Journal Article · Thu Sep 01 04:00:00 EDT 2011 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2011/09/034· OSTI ID:22277725

Hamann, Jan; Hannestad, Steen ^[1]; Raffelt, Georg G. ^[2]

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1. Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)
2. Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805 München (Germany)

We study cosmological models that contain sterile neutrinos with eV-range masses as suggested by reactor and short-baseline oscillation data. We confront these models with both precision cosmological data (probing the CMB decoupling epoch) and light-element abundances (probing the BBN epoch). In the minimal ΛCDM model, such sterile neutrinos are strongly disfavoured by current data because they contribute too much hot dark matter. However, if the cosmological framework is extended to include also additional relativistic degrees of freedom beyond the three standard neutrinos and the putative sterile neutrinos, then the hot dark matter constraint on the sterile states is considerably relaxed. A further improvement is achieved by allowing a dark energy equation of state parameter w < −1. While BBN strongly disfavours extra radiation beyond the assumed eV-mass sterile neutrino, this constraint can be circumvented by a small ν{sub e} degeneracy. Any model containing eV-mass sterile neutrinos implies also strong modifications of other cosmological parameters. Notably, the inferred cold dark matter density can shift up by 20–75% relative to the standard ΛCDM value.

• OSTI ID: 22277725
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 09 Vol. 2011; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMOLOGICAL CONSTANT
COSMOLOGICAL MODELS
COSMOLOGY
DECOUPLING
DEGREES OF FREEDOM
ELEMENT ABUNDANCE
EQUATIONS OF STATE
EV RANGE
NEUTRINOS
NONLUMINOUS MATTER
OSCILLATIONS
RELATIVISTIC RANGE
RELICT RADIATION
VISIBLE RADIATION