3 years ago

Cosmic ray $e^{+} e^{-}$ spectrum excess and peak feature observed by the DAMPE experiment from dark matter.

Bin Yue, Hong-Bo Jin, Xin Zhang, Xuelei Chen

The Chinese satellite Wukong, also known as the DArk Matter Particle Explorer (DAMPE) experiment, has released its observation data of the cosmic ray (CR) electrons and positrons, which shows an excess in the energy spectrum up to TeV energy, and possibly a peak-like structure at 1.4 TeV. We investigate the scenario that the source of the excess come from the annihilation or decay of dark matter. We consider the W$^+$W$^-$ channel and direct $e^+e^-$ channel (model A), and the double $\tau^+\tau^-$ channel and direct $e^+e^-$ channel (model B). We find that the annihilation or decay of dark matter in the galactic halo can give excellent fits to the broad excess. However, the annihilation cross section is of the order of $10^{-23} \cm^3 s^{-1}$, larger than required for obtaining the correct relic abundance. We then study whether the narrow peak at 1.4 TeV could be explained by a nearby subhalo, which thanks to the smaller distance, could supply $e^+e^-$ within a narrow energy range. We find that in order to produce a peak width less than the DAMPE energy bin width (0.2 TeV), the source must be located within $r< 0.6 \kpc$. Our global fit models do not produce the peak-like feature, instead at 1.4 TeV the spectrum show either a slope or a cliff-like feature. However, if less than optimal fit is allowed, the peak-like feature could be generated. Furthermore, an excellent fit with peak could be obtained with model B if the background is rescaled. If the dark matter decay and annihilation rates are determined using the broad excess, the required subhalo mass could be $\sim10^{5} \Msun$ for decay model with lifetime $7.3\times 10^{25}$ s, or $\sim10^{4.5} \Msun$ for annihilation model with cross-section $10^{-23} \cm^3 \mathrm{s}^{-1}$, and a shallower density profile slope $\alpha=1.2$, or $\sim10^{2.5} \Msun $ for a steep profile with $\alpha=1.7$.

Publisher URL: http://arxiv.org/abs/1712.00362

DOI: arXiv:1712.00362v2

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