Sterile neutrinos: Cosmology versus short-baseline experiments

Abstract

Cosmology and short baseline neutrino oscillation data both hint at the\nexistence of light sterile neutrinos with masses in the 1 eV range. Here we\nperform a detailed analysis of the sterile neutrino scenario using both\ncosmological and SBL data. We have additionally considered the possibility that\nthe extra neutrino degrees of freedom are not fully thermalised in the early\nuniverse. Even when analyzing only cosmological data we find a preference for\nthe existence of massive sterile neutrinos in both (3+1) and (3+2) scenarios,\nand with the inclusion of SBL data the evidence is formally at the 3.3sigma\nlevel in the case of a (3+1) model. Interestingly, cosmological and SBL data\nboth point to the same mass scale of approximately 1 eV. In the (3+1) framework\nWMAP9+SPT provide a value of the sterile mass eigenstate m_4 = (1.72 \\pm 0.65)\neV: this result is strenghtened by adding the prior from SBL posterior to m_4 =\n(1.27 \\pm 0.12) eV (m_4 = (1.23 \\pm 0.13) eV when SDSS is also considered in\nthe cosmological analysis). In the (3+2) scheme, two additional, non--fully\nthermalized, neutrinos are compatible with the whole set of cosmological and\nSBL data, leading to mass values of m_4 = (0.95 \\pm 0.30) eV and m_5 = (1.59\n\\pm 0.49) eV. The inclusion of Planck data does not change our considerations\nabout the mass scale; concerning the extra neutrino degrees of freedom,\ninvoking a partial thermalisation the 3+1 model is still consistent with the\nlatest data.\n

Keywords

Affiliated Institutions

• Istituto Nazionale di Fisica Nucleare, Sezione di Torino IT
• Aarhus University DK

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