We report calculations of cosmic-ray proton, nuclei, antiproton, electron and positron energy spectra within a “two-halo model” of diffusive transport. The two halos represent a simple, physically consistent generalization of the standard diffusion models, which assume a unique type of diffusion for cosmic rays in the whole galactic halo. We believe instead that cosmic rays may experience a smaller energy dependence of diffusion when they are in proximity of the galactic disk. Our scenario is supported by recent observations of cosmic ray protons, nuclei, anisotropy, and gamma-rays. We predict remarkably hard antiparticle spectra at high energy. In particular, at $E\gtrsim 10\mathrm{GeV}$, the antiproton/proton ratio is expected to flatten, while the positron fraction is found to increase with energy. We discuss the implications for cosmic-ray physics and dark matter searches via antimatter.

• Received 17 July 2015

DOI:https://doi.org/10.1103/PhysRevD.92.081301