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

By Jan Hamann, S. Hannestad, G. Raffelt, Y. Wong. 2011

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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 νe 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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7f90fe5c9edf9daa95887ed8cbf8ca5c17f8704a

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Citations in the corpus

Sterile Neutrino Fits to Short-Baseline Neutrino Oscillation Measurements (2012, background): “Upcoming Planck data [37] is expected to precisely measure Neff.”
A new, precise measurement of the primordial abundance of deuterium (2012, background): “If the value of (D/H)p we have deduced here is indeed the correct one, there may be no need to appeal to non-standard physics to reconcile BBN and CMB estimates of Ωb,0 (see, for example, the discussion of this point by Hamann et al. 2011).”
The Phenomenology of Right Handed Neutrinos (2013, unknown): “also [277, 278]) show a slight preference for Neff > 3, but are consistent with Neff = 3.”
Thermalisation of light sterile neutrinos in the early universe (2012, background): “However, cosmological constraints during the BBN epoch have usually been derived under the assumption that the extra sterile neutrino families were fully thermalised [26].”
Sterile neutrino oscillations: the global picture (2013, background): “The question to what extent such sterile neutrino scenarios are disfavored by cosmology and how far one would need to deviate from the ΛCDM model in order to accommodate them remains under discussion [47, 58, 59].”
Where are we with light sterile neutrinos? (2019, background): “[158] Jan Hamann, Steen Hannestad, Georg G.”