Speaker
Dr
Sergio Pastor
(IFIC (CSIC-Univ Valencia))
Description
In the framework of a 3+1 scheme, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full 4x4 mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full collision terms, as in our previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos ($N_{\rm eff}$) and its dependence on the three additional mixing angles ($\theta_{14}$, $\theta_{24}$ and $\theta_{34}$) is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very restricted by the final Planck analysis.
Primary author
Dr
Sergio Pastor
(IFIC (CSIC-Univ Valencia))
Co-authors
Dr
Pablo Fernández de Salas
(OKC (Stockholm University))
Dr
Stefano Gariazzo
(IFIC - CSIC/U. Valencia)
