Abstract
Several studies have pointed out an excess in the AMS-02 antiproton spectrum at rigidities of 10-20 GV. Its spectral properties were found to be consistent with a dark-matter particle of mass 50-100 GeV which annihilates hadronically at roughly the thermal rate. In this work, we reinvestigate the antiproton excess including all relevant sources of systematic errors. Most importantly, we perform a realistic estimate of the correlations in the AMS-02 systematic error which could potentially "fake" a dark-matter signal. The dominant systematics in the relevant rigidity range originate from uncertainties in the cross sections for absorption of cosmic rays within the detector material. For the first time, we calculate their correlations within the full Glauber-Gribov theory of inelastic scattering. The AMS-02 correlations enter our spectral search for dark matter in the form of covariance matrices which we make publicly available for the cosmic-ray community. We find that the global significance of the antiproton excess is reduced to below 1 $\sigma$ once all systematics, including the derived AMS-02 error correlations, are taken into account. No significant preference for a dark-matter signal in the AMS-02 antiproton data is found in the mass range 10-10000 GeV.
Highlights
Since their discovery about 40 years ago [1,2] cosmic-ray antiprotons have been used as a sensitive probe of exotic cosmic-ray sources in our galaxy, such as dark-matter annihilation
Since production cross sections are only known to a few percent precision, they comprise an important source of systematic errors in the modeling of antiproton fluxes
Let us turn to an example: We have tested the significance of the antiproton excess in setup 2 without including production cross section uncertainties and in a more restrictive propagation setup
Summary
Since their discovery about 40 years ago [1,2] cosmic-ray antiprotons have been used as a sensitive probe of exotic cosmic-ray sources in our galaxy, such as dark-matter annihilation. The key ingredient to test the dark-matter interpretation of the antiproton excess is a careful modeling of those systematic effects which could, alternatively, have caused the observed spectral feature To this end, strong efforts have been made to improve the prediction and to quantify the uncertainties of antiproton production by cosmic-ray scattering [15,16,17,18,19]. We carefully derive estimates for the most relevant correlations in the AMS-02 (antiproton) data and investigate their implications for the tentative dark-matter signal Appendix C summarizes the best-fit values of all involved cosmic-ray propagation parameters in the two setups considered
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