Possible Dark Matter Annihilation Signal in the AMS-02 Antiproton Data

Using the latest AMS-02 cosmic-ray antiproton flux data, we search for a potential dark matter annihilation signal. The background parameters about the propagation, source injection, and solar modulation are not assumed a priori but based on the results inferred from the recent $\mathrm{B}/\mathrm{C}$ ratio and proton data measurements instead. The possible dark matter signal is incorporated into the model self-consistently under a Bayesian framework. Compared with the astrophysical background-only hypothesis, we find that a dark matter signal is favored. The rest mass of the dark matter particles is $\sim 20–80\mathrm{GeV}$, and the velocity-averaged hadronic annihilation cross section is about $(0.2–5)\times {10}^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$, in agreement with that needed to account for the Galactic center GeV excess and/or the weak GeV emission from dwarf spheroidal galaxies Reticulum 2 and Tucana III. Tight constraints on the dark matter annihilation models are also set in a wide mass region.

Figure 1

Secondary and DM annihilation antiproton fluxes calculated for $2\sigma$ ranges of the background parameters determined in the fitting to the $\mathrm{B}/\mathrm{C}$, ${}^{10}\mathrm{Be}/{}^9\mathrm{Be}$, and proton data. As an illustration, the mass of the DM particle is 47 GeV, the cross section is ${10}^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$, and the annihilation channel is $b\overline{b}$.

Figure 2

Shaded regions and contours are the 68% and 95% credible regions, respectively, of parameters $m_{\chi }-⟨\sigma v⟩$ to fit the antiproton data, for three parameterizations of the antiproton production cross sections [39, 40, 41]. The annihilation channel is assumed to be $b\overline{b}$. Also shown are the Fermi-LAT exclusion limits from observations of dwarf spheroidal galaxies [54] and the best-fit parameters (with a rescaling of the local density) through a fitting to the Galactic center GeV excess [55].

Figure 3

The 95% credible upper limits of the DM annihilation cross section versus the mass derived through a fitting to the AMS-02 data, compared with that from Fermi-LAT observations of dwarf spheroidal galaxies [54].