  Cosmic-ray antiprotons represent an important channel for dark matter
indirect-detection studies. Current measurements of the antiproton flux at the
top of the atmosphere and theoretical determinations of the secondary
antiproton production in the Galaxy are in good agreement, with no manifest
deviation which could point to an exotic contribution in this channel.
Therefore, antiprotons can be used as a powerful tool for constraining particle
dark matter properties. By using the spectrum of PAMELA data from 50 MV to 180
GV in rigidity, we derive bounds on the dark matter annihilation cross section
(or decay rate, for decaying dark matter) for the whole spectrum of dark matter
annihilation (decay) channels and under different hypotheses of cosmic-rays
transport in the Galaxy and in the heliosphere. For typical models of galactic
propagation, the constraints are significantly strong, setting a lower bound on
the dark matter mass of a "thermal" relic at about 50-90 GeV for hadronic
annihilation channels. These bounds are enhanced to about 150 GeV on the dark
matter mass, when large cosmic-rays confinement volumes in the Galaxy are
considered, and are reduced to 4-5 GeV for annihilation to light quarks (no
bound for heavy-quark production) when the confinement volume is small. Bounds
for dark matter lighter than few tens of GeV are due to the low energy part of
the PAMELA spectrum, an energy region where solar modulation is relevant: to
this aim, we have implemented a detailed solution of the transport equation in
the heliosphere, which allowed us not only to extend bounds to light dark
matter, but also to determine the uncertainty on the constraints arising from
solar modulation modeling. Finally, we estimate the impact of soon-to-come
AMS-02 data on the antiproton constraints.
