Active-sterile neutrino oscillations in the early Universe with full collision terms

Steen Hannestad, Rasmus Sloth Hansen, Thomas Tram, Yvonne Y. Y. Wong

Research output: Contribution to journalArticlepeer-review

225 Downloads (Pure)

Abstract

Sterile neutrinos are thermalised in the early Universe via oscillations with the active neutrinos for certain mixing parameters. The most detailed calculation of this thermalisation process involves the solution of the momentum-dependent quantum kinetic equations, which track the evolution of the neutrino phase space distributions. Until now the collision terms in the quantum kinetic equations have always been approximated using equilibrium distributions, but this approximation has never been checked numerically. In this work we revisit the sterile neutrino thermalisation calculation using the full collision term, and compare the results with various existing approximations in the literature. We find a better agreement than would naively be expected, but also identify some issues with these approximations that have not been appreciated previously. These include an unphysical production of neutrinos via scattering and the importance of redistributing momentum through scattering, as well as details of Pauli blocking. Finally, we devise a new approximation scheme, which improves upon some of the shortcomings of previous schemes.
Original languageEnglish
JournalJournal of Cosmology and Astroparticle Physics
VolumeVolume 2015
Issue numberAugust 2015
DOIs
Publication statusPublished - 11 Aug 2015

Keywords

  • hep-ph
  • astro-ph.CO
  • cosmological neutrinos
  • neutrino theory
  • physics of the early universe

Fingerprint

Dive into the research topics of 'Active-sterile neutrino oscillations in the early Universe with full collision terms'. Together they form a unique fingerprint.

Cite this