A Fresh Look at keV Sterile Neutrino Dark Matter from Frozen-In Scalars

Abstract

Sterile neutrinos with a mass of a few keV can serve as cosmological warm dark matter. We study the production of keV sterile neutrinos in the early universe from the decay of a frozen-in scalar. Previous studies focused on heavy frozen-in scalars with masses above the Higgs mass leading to a hot spectrum for sterile neutrinos with masses below 8-10 keV. Motivated by the recent hints for an X-ray line at 3.55 keV, we extend the analysis to lighter frozen-in scalars, which allow for a cooler spectrum. Below the electroweak phase transition, several qualitatively new channels start contributing. The most important ones are annihilation into electroweak vector bosons, particularly W-bosons as well as Higgs decay into pairs of frozen-in scalars when kinematically allowed.

19 pages, 4 figures, model section (sec. 2) splits in effective description (sec. 2) and UV completion (sec. 5), minor changes, references added, matches published version

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Cited by in corpus (12)

• The Dawn of FIMP Dark Matter: A Review of Models and Constraints
• keV Sterile Neutrino Dark Matter from Singlet Scalar Decays: Basic Concepts and Subtle Features
• keV Sterile Neutrino Dark Matter from Singlet Scalar Decays: The Most General Case
• Long-Exposure NuSTAR Constraints on Decaying Dark Matter in the Galactic Halo
• Fundamental physics with the Hubble Frontier Fields: constraining Dark Matter models with the abundance of extremely faint and distant galaxies
• Neutrino dark matter and the Higgs portal: improved freeze-in analysis
• Real scalar phase transitions: a nonperturbative analysis
• Non-abelian Dark Matter Solutions for Galactic Gamma-ray Excess and Perseus 3.5 keV X-ray Line
• Gravitational production of sterile neutrinos
• Dark matter freeze-in via a light fermion mediator: forbidden decay and scattering
• Freeze-in and freeze-out of sterile neutrino dark matter
• Sterile neutrino Dark Matter in the minimal Dirac Seesaw