Calculation of primordial abundances of light nuclei including a heavy sterile neutrino

Abstract

We include the coupling of a heavy sterile neutrino with active neutrinos in the calculation of primordial abundances of light-nuclei. We calculate neutrino distribution functions and primordial abundances, as functions depending on a renormalization of the sterile neutrino distribution function (a), the sterile neutrino mass (ms) and the mixing angle (ϕ). Using the observable data, we set constrains on these parameters, which have the values 0a < 0.4, sin2 ϕ ≈ 0.12−0.39 and 0ms < 7 keV at 1σ level, for a fixed value of the baryon to photon ratio. When the baryon to photon ratio is allowed to vary, its extracted value is in agreement with the values constrained by Planck observations and by the Wilkinson Microwave Anisotropy Probe (WMAP). It is found that the anomaly in the abundance of 7Li persists, in spite of the inclusion of a heavy sterile neutrino.