How secret interactions can reconcile sterile neutrinos with cosmology

Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. However, such neutrinos seem incompatible with cosmology because they have too large an impact on cosmic structure formation. Here we show that new interactions in the sterile neutrino sector can prevent their production in the early Universe and reconcile short baseline oscillation experiments with cosmology.Comment: 4 pages, 5 figures, prepared for submission to PR

Sterile neutrinos with pseudoscalar self-interactions and cosmology

Sterile neutrinos in the electronvolt mass range are hinted at by a number of terrestrial neutrino experiments. However, such neutrinos are highly incompatible with data from the Cosmic Microwave Background and large scale structure. This paper discusses how charging sterile neutrinos under a new pseudoscalar interaction can reconcile eV sterile neutrinos with terrestrial neutrino data. We show that this model can reconcile eV sterile neutrinos in cosmology, providing a fit to all available data which is way better than the standard $\Lambda$CDM model with one additional fully thermalized sterile neutrino. In particular it also prefers a value of the Hubble parameter much closer to the locally measured value.Comment: 7 pages, 5 figures, uses REVTe

Cosmology with self-interacting sterile neutrinos and dark matter - A pseudoscalar model

Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. Such sterile neutrinos are incompatible with cosmology because they suppress structure formation unless they can be prevented from thermalising in the early Universe or removed by subsequent decay or annihilation. Here we present a novel scenario in which both sterile neutrinos and dark matter are coupled to a new, light pseudoscalar. This can prevent thermalisation of sterile neutrinos and make dark matter sufficiently self-interacting to have an impact on galactic dynamics and possibly resolve some of the known problems with the standard cold dark matter scenario. Even more importantly it leads to a strongly self-interacting plasma of sterile neutrinos and pseudoscalars at late times and provides an excellent fit to CMB data. The usual cosmological neutrino mass problem is avoided by sterile neutrino annihilation to pseudoscalars. The preferred value of $H_0$ is substantially higher than in standard $\Lambda$CDM and in much better agreement with local measurements.Comment: 8 pages, 4 figures, matches published versio

Pseudoscalar - sterile neutrino interactions: reconciling the cosmos with neutrino oscillations

The Short BaseLine (SBL) neutrino oscillation anomalies hint at the presenceof a sterile neutrino with a mass of around 1 eV. However, such a neutrino isincompatible with cosmological data, in particular observations of the CosmicMicrowave Background (CMB) anisotropies. However, this conclusion can change byinvoking new physics. One possibility is to introduce a secret interaction inthe sterile neutrino sector mediated by a light pseudoscalar. In thispseudoscalar model, CMB data prefer a sterile neutrino mass that is fullycompatible with the mass ranges suggested by SBL anomalies. In addition, thismodel predicts a value of the Hubble parameter which is completely consistentwith local measurements