Effects of active-sterile neutrino mixing during primordial nucleosynthesis

TL;DR

This paper investigates how sterile-active neutrino oscillations during primordial nucleosynthesis influence light-nuclei production, constraining model parameters using observational abundance data.

Contribution

It introduces a model with sterile-active neutrino mixing and a renormalization parameter, analyzing their effects on neutrino distributions and primordial element abundances.

Findings

Data favor small mixing angles.

Sterile neutrino occupation factor is constrained to be less than 0.65 at 3σ.

Model parameters are consistent with observed primordial abundances.

Abstract

In the present work, we discuss the effects of the inclusion of sterile-active neutrino oscillations during the production of primordial light-nuclei. We assume that the sterile neutrino mass-eigenstate might oscillate with the two lightest active neutrino mass- eigenstates, with mixing angles ${\phi}_1$ and ${\phi}_2$. We also allow a constant renormalization (represented by a parameter (${\zeta}$)) of the sterile neutrino occupation factor. Taking ${\zeta}$ and the mixing angles as free parameters, we have computed distribution functions of active and sterile neutrinos and primordial abundances. Using observable data we set constrains in the free parameters of the model. It is found that the data on primordial abundances are consistent with small mixing angles and with a value of ${\zeta}$ smaller than 0.65 at 3${\sigma}$ level.