Antiprotons from spallations of cosmic rays on interstellar matter

Cosmic-ray antiprotons provide an important probe for the study of Galactic dark matter, as they could be produced by neutralino annihilations, primordial black holes evaporations, or other exotic sources. On the other hand, antiprotons are anyway produced by standard nuclear reactions of cosmic-ray nuclei on interstellar matter (spallations), which are known to occur in the Galaxy. This process is responsible for a background flux that must be carefully determined to estimate the detectability of an hypothetical exotic signal. In this paper we provide a new evaluation of the interstellar cosmic antiproton flux that is fully consistent with cosmic-ray nuclei in the framework of a two-zone diffusion model. We also study and conservatively quantify all possible sources of uncertainty that may affect that antiproton flux. In particular, the primary cosmic rays are by now so well measured that the corresponding error is removed. Uncertainties related to propagation are shown to range between 10% and 25%, depending on which part of the spectrum is considered.