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Impact of semi-annihilations on dark matter phenomenology - an example of Z_N symmetric scalar dark matter

G. Bélanger, K. Kannike, A. Pukhov, M. Raidal

TL;DR

This work investigates how semi-annihilations in $Z_N$-symmetric scalar dark matter models with $N>2$ reshape DM phenomenology. By formulating minimal models with an extra doublet and a complex singlet and implementing $Z_3$ and $Z_4$ cases in micrOMEGAs, the authors quantify how semi-annihilations and inter-sector annihilations modify the relic abundance and direct-detection predictions. The study demonstrates that these nonstandard topologies can substantially change DM freeze-out and detection prospects compared to conventional $Z_2$-stabilized scenarios, with detailed results for benchmark points showing significant contributions from semi-annihilation channels and assisted freeze-out effects. The findings underscore the need to include such processes in precise relic-density calculations and in interpreting direct-detection constraints.

Abstract

We study the impact of semi-annihilations x_i x_j <-> x_k X, where x_i is any dark matter and X is any standard model particle, on dark matter phenomenology. We formulate minimal scalar dark matter models with an extra doublet and a complex singlet that predict non-trivial dark matter phenomenology with semi-annihilation processes for different discrete Abelian symmetries Z_N, N>2. We implement two such example models with Z_3 and Z_4 symmetry in micrOMEGAs and work out their phenomenology. We show that both semi-annihilations and annihilations involving only particles from two different dark matter sectors significantly modify the dark matter relic abundance in this type of models. We also study the possibility of dark matter direct detection in XENON100 in those models.

Impact of semi-annihilations on dark matter phenomenology - an example of Z_N symmetric scalar dark matter

TL;DR

This work investigates how semi-annihilations in -symmetric scalar dark matter models with reshape DM phenomenology. By formulating minimal models with an extra doublet and a complex singlet and implementing and cases in micrOMEGAs, the authors quantify how semi-annihilations and inter-sector annihilations modify the relic abundance and direct-detection predictions. The study demonstrates that these nonstandard topologies can substantially change DM freeze-out and detection prospects compared to conventional -stabilized scenarios, with detailed results for benchmark points showing significant contributions from semi-annihilation channels and assisted freeze-out effects. The findings underscore the need to include such processes in precise relic-density calculations and in interpreting direct-detection constraints.

Abstract

We study the impact of semi-annihilations x_i x_j <-> x_k X, where x_i is any dark matter and X is any standard model particle, on dark matter phenomenology. We formulate minimal scalar dark matter models with an extra doublet and a complex singlet that predict non-trivial dark matter phenomenology with semi-annihilation processes for different discrete Abelian symmetries Z_N, N>2. We implement two such example models with Z_3 and Z_4 symmetry in micrOMEGAs and work out their phenomenology. We show that both semi-annihilations and annihilations involving only particles from two different dark matter sectors significantly modify the dark matter relic abundance in this type of models. We also study the possibility of dark matter direct detection in XENON100 in those models.

Paper Structure

This paper contains 15 sections, 30 equations, 4 figures, 4 tables.

Table of Contents

  1. INTRODUCTION
  2. $Z_{N}$ LAGRANGIANS
  3. $Z_{N}$ symmetry
  4. Field content of the minimal model
  5. Constraints on charge assignments
  6. The $Z_{2}$ scalar potential
  7. $Z_{3}$ scalar potentials and particle content
  8. $Z_{4}$ scalar potentials and particle content
  9. RELIC DENSITY IN CASE OF THE $Z_3$ SYMMETRY
  10. Evolution equations
  11. Numerical results with micrOMEGAs
  12. RELIC DENSITY IN CASE OF THE $Z_4$ SYMMETRY
  13. Evolution equations
  14. Numerical results
  15. CONCLUSIONS

Figures (4)

  • Figure 1: (Left panel) $\Omega h^2$ as a function of the dark matter mass for the benchmark point with semi-annihilation (solid line), and without semi-annihilation (dashed). (Right panel) $\sigma_{x_1 \mathrm{Xe}}^{\rm SI}$ (solid). The experimental limit from XENON100 Aprile:2011hi is also displayed (dashed).
  • Figure 2: Effect of interactions between the two dark matter sectors (left) and of semi-annihilation (right) on $\Omega_1 h^2$(solid) and $\Omega_2 h^2$(dashed) as a function of $M_S$. Left panel -- Including only $\sigma_v^{1100}$ and $\sigma_v^{2200}$(black) as well as $\sigma_v^{1122}$, $\sigma_v^{2211}$ (red). Right panel -- Including only $\sigma_v^{1210}$ (green), only $\sigma_v^{1120}$ (red) as well as all semi-annihilations (blue), as a reference in black $\Omega_1 h^2$(solid) and $\Omega_2 h^2$ (dot) with only standard annihilation terms. Note that $\sigma_v^{1210}$ does not change $\Omega_1 h^2$.
  • Figure 3: Temperature evolution of $Y_1$ (solid) and $Y_2$ (dashed) with standard terms and the contribution of $\sigma_v^{1120}$ for $M_S=260$ GeV. Temperature evolution of $Y_2$ with only standard terms (green/dashed), $T$ is in GeV.
  • Figure 4: Left: $\Omega_1 h^2$(solid), $\Omega_2 h^2$(dashed) and $\Omega h^2$ (green) as a function of $M_S$, the singlet DM mass. Right: Number of events expected in XENON100 from $S$ (solid) and $H^0$ (dashed) elastic scattering as a function of $M_S$.