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

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.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [5]
  1. Department of Physics and Astronomy,Aarhus University, 8000 Aarhus C (Denmark)
  2. (Denmark)
  3. (Australia)
  4. Institute of Cosmology and Gravitation, University of Portsmouth,Portsmouth PO1 3FX (United Kingdom)
  5. School of Physics, The University of New South Wales,Sydney NSW 2052 (Australia)
Publication Date:
OSTI Identifier:
22458361
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 08; Other Information: PUBLISHER-ID: JCAP08(2015)019; OAI: oai:repo.scoap3.org:11373; Article funded by SCOAP3. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 License. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.; Country of input: International Atomic Energy Agency (IAEA)
Sponsoring Org:
SCOAP3, CERN, Geneva (Switzerland)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COLLISIONS; KINETIC EQUATIONS; MATHEMATICAL SOLUTIONS; NEUTRINO OSCILLATION; NEUTRINOS; PHASE SPACE; SCATTERING; UNIVERSE