Antiprotons from dark matter annihilation in the Galaxy: Astrophysical uncertainties

Abstract

The latest years have seen steady progresses in weakly interacting massive particle dark matter (DM) searches, with hints of possible signals suggested both in direct and indirect detection. Antiprotons play a key role in this context, since weakly interacting massive particle annihilations can be a copious source of antiprotons, and the antiproton flux from conventional astrophysical sources is predicted with fair accuracy and matches the measured cosmic ray (CR) spectrum very well. Using the publicly available dragon code, we reconsider antiprotons as a tool to set constraints on DM models; we compare against the most up-to-date $\overline{p}$ measurements, taking also into account the latest spectral information on the $p$ and He CR fluxes. In particular, we probe carefully the uncertainties associated to both standard astrophysical and DM originated antiprotons, by using a variety of distinctively different assumptions for the propagation of CRs and for the DM distribution in the Galaxy. We find that the impact of the astrophysical uncertainties on constraining the DM properties of a wide class of annihilating DM models can be much stronger, up to a factor of $\ensuremath{\sim}50$, than the one due to uncertainties on the DM distribution ($\ensuremath{\sim}2--6$). Remarkably, even reducing the uncertainties on the propagation parameters derived by local observables, nonlocal effects can change our predictions for the constraints even by 50%. Nevertheless, current $\overline{p}$ data can place tight constraints on DM models, excluding some of those suggested in connection with indirect and direct searches. Finally we discuss the impact of upcoming CR spectral data from the AMS-02 instrument on DM model constraints.