Probing Flavor Structure of Cosmic Ray $e^\mp$ Spectrum and Implications
  for Dark Matter Indirect Searches
  Measuring high energy cosmic ray electrons/positrons (CRE) provides important
means for the dark matter (DM) indirect detection and for probing the nearby
galactic sources. In this work, we perform a systematic analysis of the flavor
structure of DM annihilations into charged leptons based on the cosmic ray CRE
spectra measured by DAMPE, Fermi-LAT, AMS-02, and CALET experiments. We study
the annihilations of possible TeV scale DM particles in a nearby subhalo, which
is proposed to explain the possible peak-like structure of the DAMPE CRE data.
We pay special attention to the possible non-resonant excess (besides the
possible peak-like structure) and demonstrate that such non-resonant excess can
mainly arise from the decay of muons produced by the DM annihilations in the
subhalo. With these we study the flavor composition of the lepton final states
from DM annihilations $\chi\chi\to e^+e^-, \mu^+\mu^-, \tau^+\tau^-$ by fitting
the CRE data. We demonstrate that decays of the final states $\mu^+ \mu^-$ and
$\tau^+ \tau^-$ can provide the non-resonant excess, while the peak excess
arises from the $e^+ e^-$ final state. We further analyze the constraints on
the lepton flavor composition using the Fermi-LAT $\gamma$-ray measurements. We
find that the flavor composition is consistent with the Fermi-LAT data at
relatively low Galactic latitudes, while the fraction of the final state
$\tau^\pm$ is severely bounded.
