Cosmic Ray propagation uncertainties and Dark Matter

Dark matter particles could be detected indirectly through their annihilation into particles of the standard model, like antiprotons or positrons. This is a very challenging program for several reasons. First, one has to understand all the astrophysical processes that could also lead to the production of these antiprotons or positrons. Second, to characterize an excess it is necessary to understand the background signal, due to spallations of cosmic rays on the interstellar medium. This requires to fully understand the propagation of these charged particles in the Galaxy. Propagation is described by a diffusion equation, with other physical effects such as spallation, energy losses, diffusive reacceleration and convection. The parameters entering this equation are degenerate and there is no “standard model for cosmic ray diffusion”. As a result, the studies of indirect detection through antimatter must take into account the studies of propagation of cosmic-ray nuclei (which give constraints on the propagation parameters), which is not actually the way is is always done. Moreover, comparison of the exotic signal to the standard background must be done within the same framework, using the same equation diffusion, which unfortunately is also not actually the way is is always done.