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Asymmetric Sneutrino Dark Matter and the Omega(b)/Omega(DM) Puzzle

Dan Hooper, John March-Russell, Stephen M. West

TL;DR

The work addresses the puzzle of why the baryon and dark-matter densities are so similar by proposing a framework where dark matter carries a particle–antiparticle asymmetry tied to the baryon asymmetry through the electroweak anomaly, naturally linking $\\Omega_{\\rm b}$ and $\\Omega_{\\rm DM}$. It provides a concrete realization using mixed sneutrino dark matter in an MSSM variant with neutrino masses generated by higher-dimensional SUSY-breaking terms, and develops the relic-density formalism in the presence of asymmetry, deriving $\\Omega h^2_{\\min} = \\Omega h^2_{\\rm bary} \\frac{A}{A_{\\rm bary}} \\frac{m}{m_{\\rm bary}}$ and showing that asymmetry can expand viable parameter space. The analysis demonstrates that a viable WMAP-range relic density can be achieved in the asymmetric case for a region of sneutrino masses and mixing, with suppressed halo signals but potential Sun-capture neutrino signatures; it also outlines experimental handles via collider tests and TeV-scale resonant leptogenesis. Overall, the paper offers a natural, testable mechanism to explain the observed proximity of baryon and dark-matter densities through a shared asymmetry.

Abstract

The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. We consider models of dark matter possessing a particle-antiparticle asymmetry where this asymmetry determines both the baryon asymmetry and strongly effects the dark matter density, thus naturally linking $Ω_{\rm{b}}$ and $Ω_{\rm{dm}}$. We show that sneutrinos can play the role of such dark matter in a previously studied variant of the MSSM in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms.

Asymmetric Sneutrino Dark Matter and the Omega(b)/Omega(DM) Puzzle

TL;DR

The work addresses the puzzle of why the baryon and dark-matter densities are so similar by proposing a framework where dark matter carries a particle–antiparticle asymmetry tied to the baryon asymmetry through the electroweak anomaly, naturally linking and . It provides a concrete realization using mixed sneutrino dark matter in an MSSM variant with neutrino masses generated by higher-dimensional SUSY-breaking terms, and develops the relic-density formalism in the presence of asymmetry, deriving and showing that asymmetry can expand viable parameter space. The analysis demonstrates that a viable WMAP-range relic density can be achieved in the asymmetric case for a region of sneutrino masses and mixing, with suppressed halo signals but potential Sun-capture neutrino signatures; it also outlines experimental handles via collider tests and TeV-scale resonant leptogenesis. Overall, the paper offers a natural, testable mechanism to explain the observed proximity of baryon and dark-matter densities through a shared asymmetry.

Abstract

The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories of the early universe there is no true explanation of this fact; in particular, the baryon asymmetry and thus density depends upon unknown, and {\it a priori} unknown and possibly small, CP-violating phases which are independent of all parameters determining the dark matter density. We consider models of dark matter possessing a particle-antiparticle asymmetry where this asymmetry determines both the baryon asymmetry and strongly effects the dark matter density, thus naturally linking and . We show that sneutrinos can play the role of such dark matter in a previously studied variant of the MSSM in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms.

Paper Structure

This paper contains 6 sections, 15 equations, 2 figures.

Table of Contents

  1. Introduction
  2. The Effect of a Matter-Antimatter Asymmetry on the Density of a Thermal Relic
  3. An Example: Mixed Sneutrino Dark Matter
  4. Asymmetric sneutrino and baryon abundances
  5. Indirect Detection
  6. Conclusions

Figures (2)

  • Figure 1: The regions of parameter space which provide the quantity of mixed sneutrino cold dark matter measured by WMAP, $0.129 > \Omega_{\rm{CDM}} h^2 > 0.095$. In the left frame, the standard calculation with no matter-antimatter asymmetry is used. In the center frame the effect of a matter-antimatter asymmetry with $A/A_{\rm{bary}} \simeq 1/6$ is included, while in the right frame a matter-antimatter asymmetry $A/A_{\rm{bary}} \simeq 1/3$ is assumed. Notice the much larger regions of acceptable parameter space in cases with asymmetry. We use the following parameters: $M_1$=300 GeV, $M_2$=300 GeV, $\mu$=600 GeV, $\tan \beta=50$ and $m_h$=115 GeV. The region above the solid line is excluded by measurements of the invisible $Z$ decay width invisiblez.
  • Figure 2: The thermal relic density as a function of mass for sneutrinos+antisneutrinos with no asymmetry (dot-dash), with a matter-antimatter asymmetry of $A/A_{\rm{bary}} \simeq 1/6$ (solid) and the estimate of Eq.(\ref{['estimate']}) (dots). The relic density range favored by WMAP is bound by dashed lines ($0.129 > \Omega_{\rm{CDM}} h^2 > 0.095$). $\sin \theta$=0.3, $M_1$=300 GeV, $M_2$=300 GeV, $\mu$=600 GeV, $\tan \beta=50$ and $m_h$=115 GeV have been used. See text for details.