Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation

By Miguel Escudero. Journal of Cosmology and Astroparticle Physics, 2018

182 citations recorded by the source corpus.

The number of effective relativistic neutrino species represents a fundamental probe of the thermal history of the early Universe, and as such of the Standard Model of Particle Physics. Traditional approaches to the neutrino decoupling are either very technical and computationally expensive, or assume that neutrinos decouple instantaneously. In this work, we aim to fill the gap between these two approaches by modeling the neutrino decoupling in terms of two simple coupled differential equations for the electromagnetic and neutrino sector temperatures, in which all the relevant interactions are taken into account and which allows for a straightforward implementation of BSM species. Upon including finite temperature QED corrections we reach an accuracy on Neff in the SM of 0.01. We illustrate the usefulness of this approach to the neutrino decoupling by considering, in a model independent manner, the impact of MeV thermal dark matter on Neff. We show that Planck rules out electrophilic and neutrinophilic thermal dark matter particles of m< 3.8 MeV at 95% CL regardless of their spin, and of their annihilation being s-wave or p-wave. We point out that thermal dark matter particles with non-negligible interactions with both electrons and neutrinos are more elusive to CMB observations than purely electrophilic or neutrinophilic ones. In addition, assisted by the accuracy of our approach, we show that CMB Stage-IV experiments will generically test thermal dark matter particles with m ≲ 20 MeV. We make publicly available the codes developed for this study at this https://github.com/MiguelEA/nudec_BSM.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9871590f8b1205cb7fe54356c855489a464ef392

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Citations in the corpus

Precision early universe thermodynamics made simple: Neff and neutrino decoupling in the Standard Model and beyond (2020, methodology): “This calculation is therefore fully analogous to the one performed by the author in [1], but here we update it by accounting for next-to-leading order finite temperature corrections [42], and spin-statistics and the electron mass in the ν-ν and ν-e interaction rates.”
A precision calculation of relic neutrino decoupling (2020, methodology): “[19, 20], a simple evaluation model of Neff is proposed, including finite temperature QED corrections and neutrino oscillations.”
Neutrino decoupling including flavour oscillations and primordial nucleosynthesis (2020, methodology): “An alternative using effective equilibrium spectra for all the species involved [15, 16] allowed to obtain accurate results while reducing drastically the computation time.”
Cosmology with a very light Lμ − Lτ gauge boson (2019, background): “4 MeV after taking into account oscillations) [46, 49–51].”
Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB (2019, methodology): “• Accurately accounting for the early Universe evolution in the presence of MeV-scale states following [103, 104].”