We evaluate dark matter (DM) limits from cosmic-ray antiproton observations using the recent precise AMS-02 measurements. We properly take into account cosmic-ray propagation uncertainties, fitting DM and propagation parameters at the same time, and marginalizing over the latter. We find a significant (∼ 4.5 σ) indication of a DM signal for DM masses near 80 GeV, with a hadronic annihilation cross-section close to the thermal value, σv ≈ 3 × 10 −26 cm 3 s −1 . Intriguingly, this signal is compatible with the DM interpretation of the Galactic center gamma-ray excess. Confirmation of the signal will require a more accurate study of the systematic uncertainties, i.e., the antiproton production cross-section, and the modeling of the effect of solar modulation. Interpreting the AMS-02 data in terms of upper limits on hadronic DM annihilation, we obtain strong constraints excluding a thermal annihilation cross-section for DM masses below about 50 GeV and in the range between approximately 150 and 500 GeV, even for conservative propagation scenarios. Except for the range around ∼ 80 GeV, our limits are a factor ∼ 4 stronger than the limits from gamma-ray observations of dwarf galaxies. INTRODUCTIONCosmic-ray (CR) antiprotons are a powerful tool to investigate the particle nature of dark matter (DM), see, for example, [1][2][3][4][5][6][7][8][9][10][11][12][13]. DM constraints from CRs are, however, affected by uncertainties in the description of CR propagation in the Galaxy. Thus, CR DM limits have so far been derived for benchmark propagation models, like the MIN/MED/MAX scenarios [2] obtained from observations of the Boron over Carbon (B/C) ratio. Such benchmark models introduce an order-of-magnitude uncertainty in the DM interpretation of CR fluxes.The antiproton CR spectrum has recently been measured by the AMS-02 experiment with high precision [14]. It is thus timely to evaluate the antiproton DM constraints in the light of the new data. We will improve on previous analyses in two crucial aspects: First, the new AMS-02 data allow us to significantly reduce the uncertainties in the CR propagation. Although B/C data from AMS-02 have been recently published [15], there is, however, evidence that the propagation of heavy nuclei like B and C is different from the propagation of light nuclei like p andp [16] (but, see also [17][18][19]). Thus, using B/C data to constrain CR propagation is likely to introduce a bias when analysing antiprotons. We will instead follow the analysis of Ref. [20] (hereafter KC16) and use the measuredp flux to directly constrain the propagation scenario, thus avoiding any bias. In addition, as a second important new feature, we will constrain CR propagation including a potentialp flux from DM annihilation. Previous analyses have, in contrast, assumed a certain propagation scenario (or a small number of fixed benchmark scenarios) and thus a fixed antiproton background to then constrain a DM contribution in a second step (although, see [11] for an improved approach). Here, with a joint DM and C...

Global fits of primary and secondary cosmic-ray (CR) fluxes measured by AMS-02 have great potential to study CR propagation models and search for exotic sources of antimatter such as annihilating dark matter (DM). Previous studies of AMS-02 antiprotons revealed a possible hint for a DM signal which, however, could be affected by systematic uncertainties. To test the robustness of such a DM signal, in this work we systematically study two important sources of uncertainties: the antiproton production cross sections needed to calculate the source spectra of secondary antiprotons and the potential correlations in the experimental data, so far not provided by the AMS-02 Collaboration. To investigate the impact of cross-section uncertainties we perform global fits of CR spectra including a covariance matrix determined from nuclear cross-section measurements. As an alternative approach, we perform a joint fit to both the CR and cross-section data. The two methods agree and show that cross-section uncertainties have a small effect on the CR fits and on the significance of a potential DM signal, which we find to be at the level of 3σ. Correlations in the data can have a much larger impact. To illustrate this effect, we determine possible benchmark models for the correlations in a data-driven method. The inclusion of correlations strongly improves the constraints on the propagation model and, furthermore, enhances the significance of the DM signal up to above 5σ. Our analysis demonstrates the importance of providing the covariance of the experimental data, which is needed to fully exploit their potential.

Cosmic rays are an important tool to study dark matter annihilation in our Galaxy. Recently, a possible hint for dark matter annihilation was found in the antiproton spectrum measured by AMS-02, even though the result might be affected by theoretical uncertainties. A complementary way to test its dark matter interpretation would be the observation of low-energy antinuclei in cosmic rays. We determine the chances to observe antideuterons with GAPS and AMS-02, and the implications for the ongoing AMS-02 antihelium searches. We find that the corresponding antideuteron signal are within the GAPS and AMS-02 detection potential. If, more conservatively, the putative signal was considered as an upper limit on DM annihilation, our results would indicate the highest possible fluxes for antideuterons and antihelium compatible with current antiproton data.