A search for sterile neutrinos with the latest cosmological observations

Lu Feng,Xin Zhang,Jing-Fei Zhang

doi:10.1140/epjc/s10052-017-4986-3

Lu Feng, Xin Zhang + Show 1 more

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https://doi.org/10.1140/epjc/s10052-017-4986-3

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Abstract

We report the result of a search for sterile neutrinos with the latest cosmological observations. Both cases of massless and massive sterile neutrinos are considered in the Lambda CDM cosmology. The cosmological observations used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation data, the Hubble constant direct measurement data, the Planck Sunyaev–Zeldovich cluster counts data, the Planck lensing data, and the cosmic shear data. We find that the current observational data give a hint of the existence of massless sterile neutrino (as dark radiation) at the 1.44sigma level, and the consideration of an extra massless sterile neutrino can indeed relieve the tension between observations and improve the cosmological fit. For the case of massive sterile neutrino, the observations give a rather tight upper limit on the mass, which implies that actually a massless sterile neutrino is more favored. Our result is consistent with the recent result of neutrino oscillation experiment done by the Daya Bay and MINOS collaborations, as well as the recent result of cosmic ray experiment done by the IceCube collaboration.

Highlights

In our previous work [15], we have shown that involving a light sterile neutrino species in the CDM model can help to reconcile the tensions between Planck and above-mentioned astrophysical observations
The simplest way, for our purpose in this work, is to consider the Akaike information criterion (AIC) [78], with the definition AIC = χm2 in + 2k, where k is the number of parameters of a model
We find that the cosmic microwave background (CMB)+baryon acoustic oscillations (BAO) data can only give an upper limit, Neff < 3.44 (95.4% CL), but the CMB+BAO+other data can well constrain Neff, giving the result of Neff = 3.29+−00..1117, which indicates a detection of Neff > 0 at the 1.44σ level

Summary

Introduction

In our previous work [15], we have shown that involving a light (sub-eV) sterile neutrino species in the CDM model can help to reconcile the tensions between Planck and above-mentioned astrophysical observations (see Refs. [16,17,18,19]). The possibility of the existence of light sterile neutrinos has been motivated to explain the anomalies of short-baseline neutrino experiments [31,32,33,34,35,36,37,38,39,40]. It seems that the fully thermalized ( Neff ≈ 1) sterile neutrinos with eV-scale mass are needed to explain these results [41,42,43]. Since the sterile neutrinos have some effects on the evolution of the universe, the cosmological observations can provide independent evidence in searching for sterile neutrinos [15]

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