Sterile Neutrinos in Light of Recent Cosmological and Oscillation Data: a Multi-Flavor Scheme Approach

TL;DR

This paper performs a detailed multi-flavor analysis of sterile neutrino production, examining their cosmological and oscillation implications, and finds that (3+2) models face internal inconsistencies and are disfavored by current data.

Contribution

It introduces a comprehensive multi-flavor framework for sterile neutrino production, combining analytical and phenomenological analysis with recent oscillation and cosmological data.

Findings

(3+2) models are disfavored by internal inconsistencies in short-baseline data

Analytical description valid for small active-sterile mixing

Cosmological abundances of sterile neutrinos are contrasted with CMB and LSS data

Abstract

Light sterile neutrinos might mix with the active ones and be copiously produced in the early Universe. In the present paper, a detailed multi-flavor analysis of sterile neutrino production is performed. Making some justified approximations allows us to consider not only neutrino interactions with the primeval medium and neutrino coherence breaking effects, but also oscillation effects arising from the presence of three light (mostly-active) neutrino states mixed with two heavier (mostly-sterile) states. First, we emphasize the underlying physics via an analytical description of sterile neutrino abundances that is valid for cases with small mixing between active and sterile neutrinos. Then, we study in detail the phenomenology of (3+2) sterile neutrino models in light of short-baseline oscillation data, including the LSND and MiniBooNE results. Finally, by using the information provided by this analysis, we obtain the expected sterile neutrino cosmological abundances and then contrast them with the most recent available data from Cosmic Microwave Background and Large Scale Structure observations. We conclude that (3+2) models are significantly more disfavored by the internal inconsistencies between sterile neutrino interpretations of appearance and disappearance short-baseline data themselves, rather than by the used cosmological data.