Implications of dark matter cascade decay from DAMPE, HESS, Fermi-LAT and AMS02 data

TL;DR

This paper explores how dark matter cascade decay models can explain high-energy cosmic electron data from DAMPE, Fermi-LAT, HESS, and AMS02, fitting observed spectra while respecting gamma-ray and CMB constraints.

Contribution

It introduces a specific dark matter decay scenario into four muons as a benchmark, analyzing its fit to multiple cosmic ray data sets and constraints, and compares different cascade decay channels.

Findings

Cascade decay into four muons fits DAMPE's TeV electron spectrum.

Best-fit decay lifetime is around 10^{26} seconds, consistent with gamma-ray and CMB limits.

Additional decay channels require further spectral softening to match all data.

Abstract

Recent high-energy cosmic $e^\pm$ measurement from the DArk Matter Particle Explorer (DAMPE) satellite confirms the deviation of total cosmic ray electron spectrum above 700-900 GeV from a simple power law. In this paper we demonstrate that the cascade decay of dark matter (DM) can account for DAMPE's TeV $e^+e^-$ spectrum. We select the least constraint DM decay channel into four muons as the benchmark scenario, and perform an analysis with propagation variance in both DM signal and the Milky Way's electron background. The best-fit of the model is obtained for joint DAMPE, Fermi-Large Area Telescope (Fermi-LAT), High Energy Stereoscopic System (HESS), high energy electron data sets, and with an $\mathcal{O}(10^{26})$ second decay lifetime, which is consistent with existing gamma ray and cosmic microwave background limits. We compare the spectral difference between the cascade decay of typical final-state channels. The least constrained $4\mu$ channels give good fits to the electron spectrum's TeV scale down-turn, yet their low energy spectrum has tension with sub-TeV positron data from AMS02. We also consider a three-step cascade decay into eight muons, and also a gamma-ray constrained $4\mu,4b$ mixed channel, to demonstrate that a further softened cascade decay signal would be required for the agreement with all the data sets.