A Robust Excess in the Cosmic-Ray Antiproton Spectrum: Implications for Annihilating Dark Matter

Abstract

An excess of $\sim$10-20 GeV cosmic-ray antiprotons has been identified in the spectrum reported by the AMS-02 Collaboration. The systematic uncertainties associated with this signal, however, have made it difficult to interpret these results. In this paper, we revisit the uncertainties associated with the time, charge and energy-dependent effects of solar modulation, the antiproton production cross section, and interstellar cosmic-ray propagation. After accounting for these uncertainties, we confirm the presence of a 4.7$\ddot{I}ƒ$ antiproton excess, consistent with that arising from a $m_{\ddot{I}}‡\approx 64-88$ GeV dark matter particle annihilating to $b\bar{b}$ with a cross section of $\ddot{I}ƒv\simeq (0.8-5.2)\times 10^{-26}$ cm${}^3$/s. If we allow for the stochastic acceleration of secondary antiprotons in supernova remnants, the data continues to favor a similar range of dark matter models ($m_{\ddot{I}}‡\approx 46-94$ GeV, $\ddot{I}ƒv\approx (0.7-3.8)\times 10^{-26}$ cm${}^3/$s) with a significance of 3.3$\ddot{I}ƒ$. The same range of dark matter models that are favored to explain the antiproton excess can also accommodate the excess of GeV-scale gamma rays observed from the Galactic Center.

13 pages, 9 figures and one appendix, changes in v2 in agreement with published version, small revisions in text, results and conclusions unchanged