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The WIMP of a Minimal Technicolor Theory

Kimmo Kainulainen, Kimmo Tuominen, Jussi Virkajarvi

TL;DR

This work investigates whether a heavy fourth-family neutrino $N$ from a minimal walking technicolor theory can constitute dark matter by leveraging an early kination phase, which speeds up the expansion before BBN. It analyzes electroweak precision constraints for Dirac and Majorana realizations, finding viable regions with $m_N \sim 100$–$500$ GeV. Relic abundance is computed via the Lee–Weinberg equation under a modified expansion rate $H=\bar H_0(\frac{x}{x_0})^2\sqrt{h+r(\frac{x}{x_0})^2}$, yielding $\Omega_N \approx 0.2$ for appropriate $r$-values: $r \sim 10^{-6}$ for Majorana and $r \sim 10^{-4}$ for Dirac. Direct-detection data favor Majorana DM, which can evade current limits, while Dirac DM is constrained unless the local clustering is unusually small. Overall, the study presents Majorana fourth-generation neutrinos as a viable DM candidate within a technicolor framework, emphasizing the role of nonstandard pre-BBN expansion in achieving the observed relic density.

Abstract

We consider the possibility that a massive fourth family neutrino, predicted by a recently proposed minimal technicolor theory, could be the source of the dark matter in the universe. The model has two techniflavors in the adjoint representation of an SU(2) techicolor gauge group and its consistency requires the existence of a fourth family of leptons. By a suitable hypercharge assignement the techniquarks together with the new leptons look like a conventional fourth standard model family. We show that the new (Majorana) neutrino N can be the dark matter particle if $m_N \sim 100-500$ GeV and the expansion rate of the Universe at early times is dominated by an energy component scaling as $ρ_φ\sim a^{-6}$ (kination), with $ρ_φ/ρ_{\rm rad} \sim 10^{-6}$ during the nucleosynthesis era.

The WIMP of a Minimal Technicolor Theory

TL;DR

This work investigates whether a heavy fourth-family neutrino from a minimal walking technicolor theory can constitute dark matter by leveraging an early kination phase, which speeds up the expansion before BBN. It analyzes electroweak precision constraints for Dirac and Majorana realizations, finding viable regions with – GeV. Relic abundance is computed via the Lee–Weinberg equation under a modified expansion rate , yielding for appropriate -values: for Majorana and for Dirac. Direct-detection data favor Majorana DM, which can evade current limits, while Dirac DM is constrained unless the local clustering is unusually small. Overall, the study presents Majorana fourth-generation neutrinos as a viable DM candidate within a technicolor framework, emphasizing the role of nonstandard pre-BBN expansion in achieving the observed relic density.

Abstract

We consider the possibility that a massive fourth family neutrino, predicted by a recently proposed minimal technicolor theory, could be the source of the dark matter in the universe. The model has two techniflavors in the adjoint representation of an SU(2) techicolor gauge group and its consistency requires the existence of a fourth family of leptons. By a suitable hypercharge assignement the techniquarks together with the new leptons look like a conventional fourth standard model family. We show that the new (Majorana) neutrino N can be the dark matter particle if GeV and the expansion rate of the Universe at early times is dominated by an energy component scaling as (kination), with during the nucleosynthesis era.

Paper Structure

This paper contains 4 sections, 17 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Minimal walking technicolor and a fourth family of leptons
  3. Relic Density
  4. Conclusions

Figures (3)

  • Figure 1: Left Panel: The shaded area corresponds to the accessible range for $S$ and $T$ with the masses of the new leptons ranging from $m_Z$ to $10 m_Z$. Only the 68% confidence countour of the new global fit unknown:2005em is shown. Right Panel: The shaded area shows the overlap region from the left panel as a function of the neutral (charged) lepton mass $m_1$ ($m_2$).
  • Figure 2: Shown are the constant $\Omega_N$-contours for the Dirac (left panel) and Majorana neutrinos (right panel) in the $(m_N,r)$-plane, where $m_N$ is the mass of the neutrino and $r$ is the ratio of the dark energy and radiation energy densities at $T=1$ MeV (see Eq. (\ref{['ecosmo2']})). The area between the thick curves correspond to the observationally accepted region for the cold dark matter abundance Spergel:2006hy.
  • Figure 3: Shown are the contours of constant $\Omega_N$ which lead to a limiting detector sensitivity for a given mass $m_N$ and a local enhancement factor $k$. We used the Higgs mass $m_{H^0}=200$ GeV for the rate (\ref{['ecosmo11']}). For a given contour the area to the left from the curve is allowed. Left panel: Dirac case. Dashed line indicates the $k=1.2\times 10^4/\Omega_N$-envelope, the region above which is allowed given local dark matter density $\rho_G=0.06 \, \rm GeV/cm^3$. Right panel Majorana case.