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Tight bonds between sterile neutrinos and dark matter

Torsten Bringmann, Jasper Hasenkamp, Joern Kersten

TL;DR

The paper presents a minimal extension of the Standard Model with a spontaneously broken $U(1)_X$ dark gauge symmetry in which both CDM and sterile neutrinos are charged. A MeV-scale vector mediator generates DM self-interactions that address cusp-core and missing-satellites problems, while an eV-scale sterile neutrino provides a hot DM component consistent with cosmology and short-baseline anomalies. Thermalization of the dark sector via the Higgs portal yields the observed CDM relic density and a controlled contribution to $\Delta N_{\rm eff}$, whereas active–sterile mixing gives rise to the HDM component and can accommodate the neutrino-oscillation anomalies within the same framework. The model predicts correlated signatures in small-scale structure, CMB constraints on $N_{\rm eff}$, and neutrino experiments, offering a unified approach to both cosmology and particle physics anomalies.

Abstract

Despite the astonishing success of standard $Λ$CDM cosmology, there is mounting evidence for a tension with observations at small and intermediate scales. We introduce a simple model where both cold dark matter (DM) and sterile neutrinos are charged under a new $U(1)_X$ gauge interaction. The resulting DM self-interactions resolve the tension with the observed abundances and internal density structures of dwarf galaxies. At the ame time, the sterile neutrinos can account for both the small hot DM component favored by cosmological observations and the neutrino anomalies found in short-baseline experiments.

Tight bonds between sterile neutrinos and dark matter

TL;DR

The paper presents a minimal extension of the Standard Model with a spontaneously broken dark gauge symmetry in which both CDM and sterile neutrinos are charged. A MeV-scale vector mediator generates DM self-interactions that address cusp-core and missing-satellites problems, while an eV-scale sterile neutrino provides a hot DM component consistent with cosmology and short-baseline anomalies. Thermalization of the dark sector via the Higgs portal yields the observed CDM relic density and a controlled contribution to , whereas active–sterile mixing gives rise to the HDM component and can accommodate the neutrino-oscillation anomalies within the same framework. The model predicts correlated signatures in small-scale structure, CMB constraints on , and neutrino experiments, offering a unified approach to both cosmology and particle physics anomalies.

Abstract

Despite the astonishing success of standard CDM cosmology, there is mounting evidence for a tension with observations at small and intermediate scales. We introduce a simple model where both cold dark matter (DM) and sterile neutrinos are charged under a new gauge interaction. The resulting DM self-interactions resolve the tension with the observed abundances and internal density structures of dwarf galaxies. At the ame time, the sterile neutrinos can account for both the small hot DM component favored by cosmological observations and the neutrino anomalies found in short-baseline experiments.

Paper Structure

This paper contains 8 sections, 12 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Model setup
  3. Thermalization via the Higgs portal and decoupling of the Dark Sector
  4. Self-interacting CDM
  5. The HDM component
  6. Neutrino anomalies
  7. Discussion
  8. Conclusions

Figures (3)

  • Figure 1: Schematic overview of the cosmology implied by the model defined in Eq. \ref{['L']}.
  • Figure 2: In the yellow area, the CDM self-interaction is strong enough to flatten density cusps in the inner parts of (dwarf) galaxies Loeb:2010gj and likely also solves the too big to fail problem (as explicitly demonstrated in $N$-body simulations for parameter values corresponding to the crosses Vogelsberger:2012ku). The dark area is excluded by astrophysics Gnedin:2000eaBalberg:2002ueBuckley:2009inLoeb:2010gj. The blue band addresses the missing satellites problem Aarssen:2012fx, with a normalization that -- according to Eq. (\ref{['tkd']}) -- is proportional to $m_V\propto X_{\nu_R}^{1/2}(T_{N_1}/T)^{3/2}_{\rm kd}$. Here, we show for reference the case of $X_{\nu_R}=0.2$ and $(T_{N_1}/T)_{\rm kd}^4=0.46$.
  • Figure 3: Sterile neutrino mass $m_{N_1}$ vs. late-time additional relativistic d.o.f. $\Delta N_\text{eff}|_\text{cmb}$ and SM d.o.f. at decoupling of the ${U}(1)_{{X}}$ sector, cf. Eq. (\ref{['DNeffbbn']}). Shaded areas correspond, at $1\sigma$ and $2\sigma$ respectively, to the HDM signal Hamann:2013iba and values of $m_{N_1}$ favored by the neutrino anomalies Giunti:2013aeaGiunti:2013waa. Dashed lines indicate the minimal value of $\Delta N_\text{eff}|_\text{cmb}$ compatible with a CDM mass of, from right to left, $m_\chi=100,500,1000$ GeV. Parameter values to the left of the solid line are not achievable in the minimal scenario studied here.