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Title: Relic neutrino decoupling with flavour oscillations revisited

Abstract

We study the decoupling process of neutrinos in the early universe in the presence of three-flavour oscillations. The evolution of the neutrino spectra is found by solving the corresponding momentum-dependent kinetic equations for the neutrino density matrix, including for the first time the proper collision integrals for both diagonal and off-diagonal elements. This improved calculation modifies the evolution of the off-diagonal elements of the neutrino density matrix and changes the deviation from equilibrium of the frozen neutrino spectra. However, it does not vary the contribution of neutrinos to the cosmological energy density in the form of radiation, usually expressed in terms of the effective number of neutrinos, N{sub eff}. We find a value of N{sub eff}=3.045, in agreement with previous theoretical calculations and consistent with the latest analysis of Planck data. This result does not depend on the ordering of neutrino masses. We also consider the effect of non-standard neutrino-electron interactions (NSI), predicted in many theoretical models where neutrinos acquire mass. For two sets of NSI parameters allowed by present data, we find that N{sub eff} can be reduced down to 3.040 or enhanced up to 3.059.

Authors:
 [1];  [2];  [1]
  1. Instituto de Física Corpuscular (CSIC-Universitat de València),Parc Científic UV, C/ Catedrático José Beltrán 2, E-46980 Paterna (Valencia) (Spain)
  2. (TTK),RWTH Aachen University, D-52056 Aachen (Germany)
Publication Date:
Sponsoring Org.:
SCOAP3, CERN, Geneva (Switzerland)
OSTI Identifier:
22572124
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2016; Journal Issue: 07; Other Information: PUBLISHER-ID: JCAP07(2016)051; OAI: oai:repo.scoap3.org:16593; cc-by 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)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COLLISION INTEGRALS; COSMOLOGY; DECOUPLING; DENSITY MATRIX; ENERGY DENSITY; FLAVOR MODEL; KINETIC EQUATIONS; NEUTRINO OSCILLATION; NEUTRINO-ELECTRON INTERACTIONS; NEUTRINOS; REST MASS; SPACE VEHICLES; UNIVERSE

Citation Formats

Salas, Pablo F. de, Institute for Theoretical Particle Physics and Cosmology, and Pastor, Sergio. Relic neutrino decoupling with flavour oscillations revisited. United States: N. p., 2016. Web. doi:10.1088/1475-7516/2016/07/051.
Salas, Pablo F. de, Institute for Theoretical Particle Physics and Cosmology, & Pastor, Sergio. Relic neutrino decoupling with flavour oscillations revisited. United States. doi:10.1088/1475-7516/2016/07/051.
Salas, Pablo F. de, Institute for Theoretical Particle Physics and Cosmology, and Pastor, Sergio. 2016. "Relic neutrino decoupling with flavour oscillations revisited". United States. doi:10.1088/1475-7516/2016/07/051.
@article{osti_22572124,
title = {Relic neutrino decoupling with flavour oscillations revisited},
author = {Salas, Pablo F. de and Institute for Theoretical Particle Physics and Cosmology and Pastor, Sergio},
abstractNote = {We study the decoupling process of neutrinos in the early universe in the presence of three-flavour oscillations. The evolution of the neutrino spectra is found by solving the corresponding momentum-dependent kinetic equations for the neutrino density matrix, including for the first time the proper collision integrals for both diagonal and off-diagonal elements. This improved calculation modifies the evolution of the off-diagonal elements of the neutrino density matrix and changes the deviation from equilibrium of the frozen neutrino spectra. However, it does not vary the contribution of neutrinos to the cosmological energy density in the form of radiation, usually expressed in terms of the effective number of neutrinos, N{sub eff}. We find a value of N{sub eff}=3.045, in agreement with previous theoretical calculations and consistent with the latest analysis of Planck data. This result does not depend on the ordering of neutrino masses. We also consider the effect of non-standard neutrino-electron interactions (NSI), predicted in many theoretical models where neutrinos acquire mass. For two sets of NSI parameters allowed by present data, we find that N{sub eff} can be reduced down to 3.040 or enhanced up to 3.059.},
doi = {10.1088/1475-7516/2016/07/051},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 07,
volume = 2016,
place = {United States},
year = 2016,
month = 7
}
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  • We show that a self-consistent and coupled treatment of the weak decoupling, big bang nucleosynthesis, and photon decoupling epochs can be used to provide new insights and constraints on neutrino sector physics from high-precision measurements of light element abundances and Cosmic Microwave Background observables. Implications of beyond-standard-model physics in cosmology, especially within the neutrino sector, are assessed by comparing predictions against five observables: the baryon energy density, helium abundance, deuterium abundance, effective number of neutrinos, and sum of the light neutrino mass eigenstates. We give examples for constraints on dark radiation, neutrino rest mass, lepton numbers, and scenarios for lightmore » and heavy sterile neutrinos.« less