Cosmological search for sterile neutrinos after DESI 2024

TL;DR

This paper investigates cosmological constraints on massive sterile neutrinos using recent observational data, finding tentative evidence for their non-zero mass within certain dark energy models, but not in simpler models.

Contribution

It provides the first comprehensive analysis of sterile neutrino constraints across multiple cosmological models using combined datasets, highlighting model-dependent evidence.

Findings

Non-zero sterile neutrino mass inferred at ~2σ in w0waCDM model.

Constraints on sterile neutrino effective mass: 0.50^{+0.33}_{-0.27} eV.

Effective number of relativistic species: 3.076^{+0.011}_{-0.017}.

Abstract

The question of whether the massive sterile neutrinos exist remains a crucial unresolved issue in both particle physics and cosmology. We explore the cosmological constraints on the massive sterile neutrinos using the latest observational data, including the baryon acoustic oscillations data from DESI, the cosmic microwave background data from Planck satellite and ACT, and the 5-year Type Ia supernova data and the 3-year weak-lensing data from DES. We search for the massive sterile neutrinos within the $\Lambda$CDM, $w$CDM, and $w_0w_a$CDM models. Our analysis shows that when considering massive sterile neutrinos within the $w_0w_a\rm CDM$ model, the combined datasets allow us to infer a non-zero sterile neutrino mass at approximately $2\sigma$ confidence level. Specifically, in the $w_0w_a$CDM+Sterile model, the effective mass of sterile neutrinos and the effective number of relativistic species are constrained to be $m_{\nu,\ \mathrm{sterile}}^{\mathrm{eff}} = 0.50^{+0.33}_{-0.27} \, \mathrm{eV}$ and $N_\mathrm{eff} = 3.076^{+0.011}_{-0.017}$, respectively. However, the $\Lambda$CDM+Sterile and $w$CDM+Sterile models could not provide evidence supporting the existence of massive sterile neutrinos.