Join us for AstroParticle Lunch! This week's presentation will be led by Jan Heisig, from the CP3 Center in Louvain.
Abstract:
Cosmic-ray observations provide a powerful probe of dark-matter annihilation in the Galaxy. In this talk I present recent analyses of the AMS-02 antiproton data, reducing cosmic-ray propagation uncertainties by fitting at the same time dark-matter and cosmic-ray propagation parameters. The resulting bounds are among the strongest for heavy dark matter, while for smaller masses, around or below 100 GeV, the analysis exhibits a possible hint for an annihilation signal. Interestingly, the signal is compatible with a thermal annihilation cross-section for frozen-out dark matter as well as a dark-matter interpretation of the gamma-ray Galactic center excess. We examine the robustness of this hint by studying the effect of the most important systematic uncertainties: the antiproton production cross sections needed to calculate the source spectra of secondary antiprotons and the potential correlations in the experimental measurements, so far not provided by the AMS-02 Collaboration. While the impact of production cross-section uncertainties is mild, correlation in the AMS-02 data turn out to be decisive and can largely alter the significance of the finding in both directions. The dominant systematics in the rigidity region of interest, around 10-20 GV, arises from uncertainties in the cross-sections for cosmic-ray absorption in the AMS-02 detector, the measured flux is corrected for. We compute the corresponding correlations by a careful re-evaluation of the involved absorption cross-sections within the Glauber-Gribov model. These correlations diminish the statistical preference for the additional contribution from dark matter. At the same time they enable to further exploit the precision of the AMS-02 data in order to constrain cosmic-ray propagation models.