Antiprotons and cosmic-ray propagation in the galaxy

Based on our three-dimensional cosmic-ray (CR) propagation model, we study the behavior of CR antiprotons (CR-(p) over bar 's), and compare our numerical results with recent experimental data, particularly those obtained by the BESS group. There is a common perception that diffusion-reacceleration models produce too low a (p) over bar flux below 5 GeV. However, we find that the BESS data are compatible with a model including the reacceleration process in the energy region greater than or similar to 1 GeV, if we adopt Galactic parameters that reproduce the CR data for primary components (protons, helium, etc.), secondary components (B, sub-Fe), and CR isotopes (Be-10, Be-26, etc.). This indicates that most CR-(p) over bar 's are secondary products of collisions between CRs and the interstellar medium (ISM) gas. However, because of poor statistics, we could not confirm whether or not BESS data with energies less than 1 GeV are consistent with those expected from other CR components, even taking the modulation effect into account. Nevertheless, it is important to determine the intensity of CR-(p) over bar 's expected from the rich CR data now available, for studies of (p) over bar 's of cosmological origin, such as the evaporation of primordial black holes and/or the annihilation of supersymmetiric dark matter particles.