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Positrons and antiprotons from inert doublet model dark matter

Emmanuel Nezri, Michel H. G. Tytgat, Gilles Vertongen

TL;DR

The paper assesses whether a minimal scalar dark matter candidate in the Inert Doublet Model can account for antimatter signals in cosmic rays reported by PAMELA, ATIC, and HESS. Using DarkSUSY and micrOMEGAs, it computes $e^+$ and $\bar{p}$ fluxes from IDM annihilation across three mass regimes, incorporating diffusion/solar modulation, an NFW halo, and possible boost factors or Sommerfeld enhancements. It finds that a $M_{DM} \approx 10$ GeV candidate can yield sizable antimatter fluxes (with notable anti-deuteron predictions) only if a boost is present and solar modulation is favorable; a $M_{DM} \approx 70$ GeV candidate generally cannot explain the data, while a $M_{DM} \sim$ TeV with large enhancements could fit PAMELA but not ATIC. Overall, IDM struggles to jointly explain PAMELA and ATIC, though it makes distinctive, testable predictions for light DM anti-deuterons and for heavy DM scenarios with large boost factors.

Abstract

In the framework of the Inert Doublet Model, a very simple extension of the Standard Model, we study the production and propagation of antimatter in cosmic rays coming from annihilation of a scalar dark matter particle. We consider three benchmark candidates, all consistent with the WMAP cosmic abundance and existing direct detection experiments, and confront the predictions of the model with the recent PAMELA, ATIC and HESS data. For a light candidate, M_{DM} = 10 GeV, we argue that the positron and anti-proton fluxes may be large, but still consistent with expected backgrounds, unless there is an enhancement (boost factor) in the local density of dark matter. There is also a substantial anti-deuteron flux which might be observable by future experiments. For a candidate with M_{DM} = 70 GeV, the contribution to positron and anti-proton fluxes is much smaller than the expected backgrounds. Even if a boost factor is invoked to enhance the signals, the candidate is unable to explain the observed positron and anti-proton excesses. Finally, for a heavy candidate, M_{DM} = 10 TeV, it is possible to fit the PAMELA excess (but, unfortunately, not the ATIC one) provided there is a large enhancement, either in the local density of dark matter or through the Sommerfeld effect.

Positrons and antiprotons from inert doublet model dark matter

TL;DR

The paper assesses whether a minimal scalar dark matter candidate in the Inert Doublet Model can account for antimatter signals in cosmic rays reported by PAMELA, ATIC, and HESS. Using DarkSUSY and micrOMEGAs, it computes and fluxes from IDM annihilation across three mass regimes, incorporating diffusion/solar modulation, an NFW halo, and possible boost factors or Sommerfeld enhancements. It finds that a GeV candidate can yield sizable antimatter fluxes (with notable anti-deuteron predictions) only if a boost is present and solar modulation is favorable; a GeV candidate generally cannot explain the data, while a TeV with large enhancements could fit PAMELA but not ATIC. Overall, IDM struggles to jointly explain PAMELA and ATIC, though it makes distinctive, testable predictions for light DM anti-deuterons and for heavy DM scenarios with large boost factors.

Abstract

In the framework of the Inert Doublet Model, a very simple extension of the Standard Model, we study the production and propagation of antimatter in cosmic rays coming from annihilation of a scalar dark matter particle. We consider three benchmark candidates, all consistent with the WMAP cosmic abundance and existing direct detection experiments, and confront the predictions of the model with the recent PAMELA, ATIC and HESS data. For a light candidate, M_{DM} = 10 GeV, we argue that the positron and anti-proton fluxes may be large, but still consistent with expected backgrounds, unless there is an enhancement (boost factor) in the local density of dark matter. There is also a substantial anti-deuteron flux which might be observable by future experiments. For a candidate with M_{DM} = 70 GeV, the contribution to positron and anti-proton fluxes is much smaller than the expected backgrounds. Even if a boost factor is invoked to enhance the signals, the candidate is unable to explain the observed positron and anti-proton excesses. Finally, for a heavy candidate, M_{DM} = 10 TeV, it is possible to fit the PAMELA excess (but, unfortunately, not the ATIC one) provided there is a large enhancement, either in the local density of dark matter or through the Sommerfeld effect.

Paper Structure

This paper contains 12 sections, 28 equations, 10 figures.

Table of Contents

  1. Introduction
  2. The Inert Doublet Model
  3. Antimatter in Cosmic Rays
  4. Anti-protons
  5. Positrons
  6. Solar modulation
  7. Dark Matter annihilation
  8. The IDM vs the PAMELA, ATIC and HESS observations
  9. Low mass range
  10. Middle mass range
  11. High mass range
  12. Conclusion

Figures (10)

  • Figure 1: Branching ratios of the $H_0$ annihilation as a function of $M_{H_0}$. The Higgs mass $M_h$ is fixed at 120 GeV. Left panel: $\mu_2=40$ GeV; Right panel: $\mu_2=200$ GeV.
  • Figure 2: Left panel: Positron fraction measured by balloon experiments and PAMELA (in red). Centre panel: Total electron and positron flux measured by balloon experiments, in particular ATIC, together with the HESS data. Right panel: $\bar{p}/p$ fraction. In all cases the red (blue) lines represent the expected background from Eq. (13-15) and Eq. (8-9) for leptons and baryons respectively without (with) a solar modulation of $\phi = 500$ MV.
  • Figure 3: Left panel : The thin curve represents the positron fraction generated by a fiducial flux of positron $\Phi(E) = 6.5 \cdot10^5 \, E^{-2.1}$ GeV$^{-1}$ cm$^{-2}$ s$^{-1}$ sr$^{-1}$. Right panel : Expected total electron plus positron flux in comparison with the ATIC measurements. In both panels, the thick plain lines represent the backgrounds, whereas (thick) dashed lines represents the signals (+ bgd).
  • Figure 4: A Low Mass candidate ($M_{DM}=10$ GeV). Thick Plain: Background, (Thick) Dashed: Signal (+ BckGrd) and (Thick) Dotted: Signal with boost factor = 10 (+ BckGrd). A solar modulation of $\phi = 500$ MV has been applied.
  • Figure 5: Left panel (Right panel) : Flux of positrons (anti-protons) for $M_{DM}=10$ GeV. Thick Plain: Background, (Thick) Dashed: Signal (+ BckGrd) and (Thick) Dotted: Signal with boost factor = 10 (+ BckGrd). The red (blue) curve corresponds to signals without (with) solar modulation ($\phi = 500$ MV).
  • ...and 5 more figures