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Upgrading Sterile Neutrino Dark Matter to FI$m$P Using Scale Invariance

Zhaofeng Kang

TL;DR

The paper develops FI$m$P, a framework that merges feebly interacting dark matter with scale invariance, as realized in the scale-invariant νSISM with three right-handed neutrinos and two scalar singlets. Scale invariance is dynamically broken via radiative effects along a flat direction, yielding a Goldstone boson and two heavy Higgs states, while the Coleman–Weinberg potential endows a pseudo-Goldstone boson with mass. The lightest RHN, $N_1$, is produced non-thermally through singlet decays (freeze-in), and, aided by a flavor-structured RHN sector and multiple singlets, can obtain the correct relic density across a broad parameter space. Importantly, freeze-in production can accommodate a keV-scale $N_1$ without conflicting with X-ray or Ly-$ ext{α}$ bounds, and the model predicts additional Higgs states and a PGSB that could be probed experimentally.

Abstract

In this article we propose a class of extremely light feebly interacting massive particle, FI$m$Ps. They are combination of feebly interacting massive particle with scale invariance, by which DM stability, mass origin and relic density are inherently related. In the scale invariant version of the Standard Model (SM) with three right-handed neutrinos ($ν$SISM), the lightest $N_1$ realizes the FI$m$P scenario. In this example scalar singlets, which are intrinsic to the $ν$SISM, generate mass and relic density for this FI$m$P simultaneously. Moreover, they are badly needed for electroweak symmetry spontaneously breaking. Interestingly, a 7.1 keV $N_1$ with correct relic density, that can explain the recent 3.55 keV $X-$ray line, lies in the bulk parameter space of our model.

Upgrading Sterile Neutrino Dark Matter to FI$m$P Using Scale Invariance

TL;DR

The paper develops FIP, a framework that merges feebly interacting dark matter with scale invariance, as realized in the scale-invariant νSISM with three right-handed neutrinos and two scalar singlets. Scale invariance is dynamically broken via radiative effects along a flat direction, yielding a Goldstone boson and two heavy Higgs states, while the Coleman–Weinberg potential endows a pseudo-Goldstone boson with mass. The lightest RHN, , is produced non-thermally through singlet decays (freeze-in), and, aided by a flavor-structured RHN sector and multiple singlets, can obtain the correct relic density across a broad parameter space. Importantly, freeze-in production can accommodate a keV-scale without conflicting with X-ray or Ly- bounds, and the model predicts additional Higgs states and a PGSB that could be probed experimentally.

Abstract

In this article we propose a class of extremely light feebly interacting massive particle, FIPs. They are combination of feebly interacting massive particle with scale invariance, by which DM stability, mass origin and relic density are inherently related. In the scale invariant version of the Standard Model (SM) with three right-handed neutrinos (SISM), the lightest realizes the FIP scenario. In this example scalar singlets, which are intrinsic to the SISM, generate mass and relic density for this FIP simultaneously. Moreover, they are badly needed for electroweak symmetry spontaneously breaking. Interestingly, a 7.1 keV with correct relic density, that can explain the recent 3.55 keV ray line, lies in the bulk parameter space of our model.

Paper Structure

This paper contains 16 sections, 40 equations, 2 figures.

Table of Contents

  1. introduction and motivation
  2. The scale invariant version of $\nu$SM ($\nu$SISM)
  3. Scale invariance spontaneously breaking
  4. Flat direction and tree level spectrum
  5. CW potential and pseudo-GSB mass
  6. Freeze-in Sterile Neutrino
  7. A toy analysis
  8. Consider multi-singlets $\&$ flavor structure
  9. The numerical analysis of the $\nu$SISM
  10. On the Higgs bosons
  11. On the FI$m$P with a benchmark at 3.5 keV $X-$ray line
  12. Conclusion and discussion
  13. Acknowledgements
  14. The most general scalar potential: from complex to real
  15. Free streaming scale
  16. ...and 1 more sections

Figures (2)

  • Figure 1: Left: Contour plots of masses of the SM-like Higgs boson (red thick lines, two values 123 GeV and 126 GeV taken), heaviest Higgs boson $m_{H_2}$ (black thick lines) and PGSB (dotted thick). The dashed lines are for different choices of the values of $\lambda_\sigma$: 0.5, 2, 4. The green-shadowed region has been excluded by the BEFB condition. We take $y=5$ and $x=0.8$, $\lambda_h=0.78$. Right: The same but with $y=3$ for comparison.
  • Figure 2: In this plot, the shadowed region is excluded by the $X-$ray observations, and the vertical line at $M_{N_1}=3$ keV indicates the lower bound on $M_{N_1}$ from the free streaming limit. On the line with lepton asymmetry $L=0$, correct relic density of $N_1$ is achieved via the DW mechanism; While on the line with $L=1.24\times 10^{-4}$, it is via resonant production (we use data from Ref. Canetti:2012kh). The red star labelling the point that fits the 3.55 keV $X-$ray anomaly. It lies in the bulk parameter space of the freeze-in scenario.