Neutrino masses and the number of neutrino species from WMAP and 2dFGRS

By S. Hannestad. 2003

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We have performed a thorough analysis of the constraints which can be put on neutrino parameters from cosmological observations, most notably those from the WMAP satellite and the 2dF galaxy survey. For these data we find an upper limit on the sum of active neutrino mass eigenstates of ∑mν ≤ 1.0 eV (95% conf.), but this limit is dependent on priors. We find that the WMAP and 2dF data alone cannot rule out the evidence from neutrinoless double beta decay reported by the Heidelberg–Moscow experiment. In terms of the relativistic energy density in neutrinos or other weakly interacting species we find, in units of the equivalent number of neutrino species, Nν, that Nν = 4.0+3.0−2.1 (95% conf.). When BBN constraints are added, the bound on Nν is 2.6+0.4−0.3 (95% conf.), suggesting that Nν could possibly be lower than the standard model value of 3. This can, for instance, be the case in models with very low reheating temperature and incomplete neutrino thermalization. Conversely, if Nν is fixed to 3 then the data from WMAP and 2dFGRS predict that 0.2458 ≤ YP ≤ 0.2471 (95% conf.), which is significantly higher than the observationally measured value. The limit on relativistic energy density changes when a small νe chemical potential is present during BBN. In this case the upper bound on Nν from WMAP, 2dFGRS and BBN is Nν ≤ 6.5. Finally, we find that a non-zero ∑mν can be compensated by an increase in Nν. One result of this is that the LSND result is not yet ruled out by cosmological observations.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/417f903aa5356555b50d1dbbfaf79e0d3b39913e

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FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2008, unknown): “…the extra relativistic degrees of freedom in the universe, using the cosmological probes such as CMB and the large-scale structure (Pierpaoli 2003; Hannestad 2003; Crotty et al. 2003, 2004; Barger et al. 2003; Trotta & Melchiorri 2005; Lattanzi et al. 2005; Cirelli & Strumia 2006; Hannestad…”
The Three-Dimensional Power Spectrum of Galaxies from the Sloan Digital Sky Survey (2003, background): “…& Strauss 1998) can provide powerful constraints on the Hubble parameter (Eisenstein et al. 1998) and accurate determination of the shape of P (k) can place strong constraints on neutrino masses (Hu et al. 1998; Spergel et al. 2003; Hannestad 2003) and help pin down the primordial power spectrum.”
Neutrino Mass Ordering from Oscillations and Beyond: 2018 Status and Future Prospects (2018, methodology): “…data is to use the information contained in the full-shape of the galaxy power spectrum (see e.g., Allen et al., 2003; Elgaroy and Lahav, 2003; Hannestad, 2003; Spergel et al., 2003; Barger et al., 2004; Crotty et al., 2004; Hannestad and Raffelt, 2004; Tegmark et al., 2004, 2006; Fogli et…”
Proton stability in grand unified theories, in strings and in branes (2006, unknown): “while the WMAP collaboration gives [416,417] ∑”
The Atacama Cosmology Telescope: cosmological parameters from three seasons of data (2013, unknown): “…from scale invariance have been tested in a variety of models and contexts (e.g., Wang et al. 1999; Tegmark & Zaldar-riaga 2002; Bridle et al. 2003; Hannestad 2003; Martin & Ringeval 2004a,b; Sealfon et al. 2005; Spergel et al. 2007; Verde & Peiris 2008; Peiris & Verde 2010; V´azquez et al. 2012),…”