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

Abstract

We revisit the upper bound on the annihilation cross-section, $\langle\sigma v\rangle$ of a stable dark matter (DM) of mass $500-10^{14}$ GeV by considering five different channels: $W^+W^-$, $b\bar{b}$, $\mu^+\mu^-$, $\tau^+\tau^-$, 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 $W^+W^-$, $b\bar{b}$, $\mu^+\mu^-$, $\tau^+\tau^-$, and $e^+e^-$ and derive the corresponding lower bound on the DM lifetime, $\tau_{\rm DM}$. We find that the latest AMS-02 data provide the most stringent constraints on $\langle\sigma v\rangle$ for DM masses below 2 TeV, while HESS yields the strongest limits for $M_{\rm DM}\gtrsim2$ TeV. The HESS gives a much more stringent limit on the DM lifetime, excluding $\tau_{\rm DM\rightarrow\mu^+\mu^-}\lesssim\mathcal{O}(10^{30})$ s for a 10 TeV mass of DM. The limits on $\langle\sigma v\rangle$ derived from the $e^+e^-$ flux are competitive with those from $\gamma$-ray and neutrino observations for DM masses in the range $10^5$--$10^{11}$ GeV, and become the most stringent beyond this range. For decaying DM, the $e^+e^-$ flux provides the strongest constraints on the DM lifetime over the mass range $10^3$--$10^9$ GeV.