Are Light Sterile Neutrinos Preferred or Disfavored by Cosmology?

TL;DR

This paper investigates whether cosmological data supports or disfavors the existence of eV-mass sterile neutrinos, highlighting the dependence on dataset choices and systematic uncertainties, and finding mixed results based on analysis methods.

Contribution

It provides a comprehensive analysis of cosmological constraints on sterile neutrinos, emphasizing the impact of dataset selection and systematic uncertainties on their viability.

Findings

Sterile neutrino model is favored with MLCS supernova fitter.

Disfavored with SALT2 supernova fitter by  in 
2 datasets.

Excluding supernova data, the model is mildly disfavored, suggesting dataset choice critically affects conclusions.

Abstract

We find that the viability of a cosmological model that incorporates 2 sterile neutrinos with masses around 1 eV each, as favored by global neutrino oscillation analyses including short baseline results, is significantly dependent on the choice of datasets included in the analysis and the ability to control the systematic uncertainties associated with these datasets. Our analysis includes a variety of cosmological probes including the cosmic microwave background (WMAP7+SPT), Hubble constant (HST), galaxy power spectrum (SDSS-DR7), and supernova distances (SDSS and Union2 compilations). In the joint observational analysis, our sterile neutrino model is equally favored as a LCDM model when using the MLCS light curve fitter for the supernova measurements, and strongly disfavored by the data at \Delta\chi^2 ~ 18 when using the SALT2 fitter. When excluding the supernova measurements, the sterile neutrino model is disfavored by the other datasets at \Delta\chi^2 ~ 12, and at best becomes mildly disfavored at \Delta\chi^2 ~ 3 when allowing for curvature, evolving dark energy, additional relativistic species, running of the spectral index, and freedom in the primordial helium abundance. No single additional parameter accounts for most of this effect. Therefore, if laboratory experiments continue to favor a scenario with roughly eV mass sterile neutrinos, and if this becomes decisively disfavored by cosmology, then a more exotic cosmological model than explored here may become necessary.