Flavor structure of the cosmic-ray electron/positron excesses at DAMPE

The Dark Matter Particle Explorer (DAMPE) satellite detector announced its first result for measuring the cosmic-ray electron/positron (CRE) energy spectrum up to 4.6 TeV, including a tentative peak-like event excess at (1.3-1.5) TeV. In this work, we uncover a significant hidden excess in the DAMPE CRE spectrum over the energy range (0.6-1.1) TeV, which has a non-peak-like structure. We propose a new mechanism to explain this excess by a set of 1.5 TeV μ± events with subsequent decays into e± plus neutrinos. For explaining this new excess together with the peak excess around 1.4 TeV, we demonstrate that the flavor structure of the original lepton final-state produced by dark matter (DM) annihilations (or other mechanism) should have a composition ratio Ne:(Nμ+16Nτ)=1:y, with y≃2.6-10.8. For lepton portal DM models, this puts nontrivial constraint on the lepton-DM-mediator couplings λe:(λμ4+16λτ4)14=1:y14 with a narrow range y14≃1.3-1.8.