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Revisiting the limits on dark matter annihilation cross-section and decay lifetime in light of electron and positron fluxes

Nagisa Hiroshima, Kazunori Kohri, Partha Kumar Paul, Narendra Sahu

TL;DR

This study targets indirect detection constraints on heavy dark matter by analyzing all-electron fluxes and accompanying gamma-ray data across DM masses from $500~\mathrm{GeV}$ to $10^{16}~\mathrm{GeV}$ for two-body SM final states $W^+W^-$, $b\bar b$, $\mu^+\mu^-$, $\tau^+\tau^-$, and $e^+e^-$. It employs a steady-state diffusion framework to propagate DM-induced $e^\pm$ through the Galaxy, using a semi-analytic flux formula with a halo function $I(\lambda_D)$ under a min-NFW halo and including electroweak corrections via the $dN_{e^\pm}/dE$ spectra. A chi-square analysis against data from CALET, AMS-02, DAMPE, HESS, HAWC, GRAPES-3, and CASA-MIA yields 95% CL limits on $\langle\sigma v\rangle$ and $\tau_{\rm DM}$ over the full mass range, with CALET dominating low-mass cross-section bounds, AMS-02 constraining low-mass lifetimes, and HAWC/CASA-MIA governing high-mass limits. The results extend the indirect-detection landscape up to $M_{\rm DM}=10^{16}$ GeV and provide benchmarks such as $\langle\sigma v\rangle_{\rm DM\rightarrow\mu^+\mu^-} \lesssim O(10^{-24})~\mathrm{cm^3/s}$ and $\tau_{\rm DM\rightarrow\mu^+\mu^-} \gtrsim O(10^{27})~\mathrm{s}$ at 1 TeV, highlighting the complementary reach of current observatories and guiding future experimental efforts.

Abstract

We revisit the upper bound on the annihilation cross-section, $\langleσv\rangle$ of a stable dark matter (DM) of mass $5\times10^2-10^{14}$ GeV by considering five different channels: $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$. We use the observed electron and positron fluxes from CALET, DAMPE, HESS, positron flux from AMS-02, and gamma-ray flux from HAWC, GRAPES-3, CASA-MIA to constrain the annihilation cross-section. We also consider unstable DM of mass $10^3-10^{16}$~GeV decaying to $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$ and derive the corresponding lower bound on the DM lifetime, $τ_{\rm DM}$. We find that the latest data from CALET gives a stringent constraint on $\langleσv\rangle$ in the low DM mass regime. For a typical DM mass of 1 TeV, we show that $\langleσv\rangle_{{\rm DM~DM}\rightarrowμ^+μ^-}\gtrsim\mathcal{O}(10^{-24})~\rm cm^3/s$ is disfavored. On the other hand in the low mass regime, the AMS-02 gives a much stringent limit on the DM lifetime, excluding $τ_{\rm DM\rightarrowμ^+μ^-}\lesssim\mathcal{O}(10^{27})$ s for a 1 TeV mass of DM. In the high mass regime, typically $M_{\rm DM}\gtrsim\mathcal{O}(10^5)$ GeV, HAWC and CASA-MIA give the strongest constraints on $\langleσv\rangle$ and $τ_{\rm DM}$.

Revisiting the limits on dark matter annihilation cross-section and decay lifetime in light of electron and positron fluxes

TL;DR

This study targets indirect detection constraints on heavy dark matter by analyzing all-electron fluxes and accompanying gamma-ray data across DM masses from to for two-body SM final states , , , , and . It employs a steady-state diffusion framework to propagate DM-induced through the Galaxy, using a semi-analytic flux formula with a halo function under a min-NFW halo and including electroweak corrections via the spectra. A chi-square analysis against data from CALET, AMS-02, DAMPE, HESS, HAWC, GRAPES-3, and CASA-MIA yields 95% CL limits on and over the full mass range, with CALET dominating low-mass cross-section bounds, AMS-02 constraining low-mass lifetimes, and HAWC/CASA-MIA governing high-mass limits. The results extend the indirect-detection landscape up to GeV and provide benchmarks such as and at 1 TeV, highlighting the complementary reach of current observatories and guiding future experimental efforts.

Abstract

We revisit the upper bound on the annihilation cross-section, of a stable dark matter (DM) of mass GeV by considering five different channels: , , , , and . We use the observed electron and positron fluxes from CALET, DAMPE, HESS, positron flux from AMS-02, and gamma-ray flux from HAWC, GRAPES-3, CASA-MIA to constrain the annihilation cross-section. We also consider unstable DM of mass ~GeV decaying to , , , , and and derive the corresponding lower bound on the DM lifetime, . We find that the latest data from CALET gives a stringent constraint on in the low DM mass regime. For a typical DM mass of 1 TeV, we show that is disfavored. On the other hand in the low mass regime, the AMS-02 gives a much stringent limit on the DM lifetime, excluding s for a 1 TeV mass of DM. In the high mass regime, typically GeV, HAWC and CASA-MIA give the strongest constraints on and .

Paper Structure

This paper contains 7 sections, 9 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Electron and Positron Excesses from DM Annihilation and decay
  3. Production and propagation of positron and electron
  4. Background fluxes of electron and positron
  5. Result and discussions
  6. Conclusions and future outlook
  7. Annihilation cross-section and lifetime constraints for $b\bar{b}$, $e^+e^-$, $\mu^+\mu^-$, $\tau^+\tau^-$ channels

Figures (4)

  • Figure 1: Left: Total electron flux ($e^-+e^+$) from DM annihilation into the $W^+W^-$ channel for $M_{\rm DM}=10^3$ GeV (blue solid), $10^5$ GeV (blue dashed), and $10^{10}$ GeV (blue dash-dotted). The curves correspond to the annihilation cross-sections at the 95% C.L. limit, with values of $1.16\times10^{-23}~\rm cm^3/s$, $1.83\times10^{-21}~\rm cm^3/s$, and $2.85\times10^{-13}~\rm cm^3/s$ for these respective masses. The red cross represent the CALET electron flux data CALET:2023emo. The gray shaded region is the all electron background including the secondaries, distant supernovae, and electron flux from all pulsars taken from CALET:2023emo. Right: Total electron flux from DM decay into the $W^+W^-$ channel for $M_{\rm DM}=10^3$ GeV (blue solid), $10^5$ GeV (blue dashed), and $10^{10}$ GeV (blue dash-dotted). The curves correspond to the decay lifetime at the 95% C.L. limit, with values of $2.77\times10^{26}~\rm s$, $2.20\times10^{26}~\rm s$, and $2.09\times10^{23}~\rm s$ for these respective masses.
  • Figure 2: 95% C.L. limits on DM annihilation cross-section (left) and DM lifetime (right) from CALET, AMS-02, HAWC, GRAPES-3, CASA-MIA, DAMPE, and H.E.S.S. for $W^+W^-$ channel. The black dashed-dotted horizontal line represent the approximate value of the canonical of the annihilation cross-section corresponding to the “ WIMP miracle”, $\langle\sigma v\rangle=3\times10^{-26}~\rm cm^3/s$Steigman:2012nbSaikawa:2020swg. The gray dashed line depict the unitarity limit, see text for more details.
  • Figure 3: Left: Summary of 95% C.L. limits on DM annihilation cross-section, $\langle\sigma v\rangle$ as a function of DM mass, $M_{\rm DM}$ for AMS-02, CALET, HAWC, and CASA-MIA are shown. Right: Summary of 95% C.L. limits on DM lifetime, $\tau_{\rm DM}$ as a function of DM mass, $M_{\rm DM}$ for AMS-02, CALET, HAWC, and CASA-MIA are shown.
  • Figure 4: 95% C.L. limits on DM annihilation cross-section (left) and DM lifetime (right) from CALET, AMS-02, HAWC, GRAPES-3, CASA-MIA, DAMPE, and H.E.S.S. for various channels. From top to bottom, we show the cases of $\mu^+\mu^-$, $b\bar{b}$, $\tau^+\tau^-$, and $e^+e^-$. Each line corresponds to a different experiment.