Relic neutrino decoupling with flavour oscillations revisited

By P. F. de Salas, S. Pastor. 2016

372 citations recorded by the source corpus.

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, Neff. We find a value of Neff = 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 Neff can be reduced down to 3.040 or enhanced up to 3.059.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/8304b63f427cca140cd0ee7037aed44b7490b112

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In Nuclear and High Energy Physics

Citations in the corpus

Cosmology Intertwined II: The Hubble Constant Tension (2020, neutral): “[217] P.”
Precision early universe thermodynamics made simple: Neff and neutrino decoupling in the Standard Model and beyond (2020, methodology): “This result is in excellent agreement with state-of-the-art calculations ofNeff in the SM [28, 29] that account for non-thermal corrections to the neutrino distribution functions and neutrino oscillations.”
Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation (2018, methodology): “045 obtained in [5], a pertinent comment is that our evaluation takes .”
Flavor structures of charged fermions and massive neutrinos (2019, background): “046 predicted by the standard cosmological model [326, 327].”
A precision calculation of relic neutrino decoupling (2020, methodology): “Then, in this paper, by solving the kinetic equations for massive neutrinos in the early Universe, we study the distortions for neutrino spectra in the mass basis too, which could be easily extrapolated to those in the current epoch, and compare the results both in the flavor and mass bases.”