Cosmicp¯Production in InterstellarppCollisions

We place a conservative upper limit of ∼ 4.6 × ${10}^{-4\mathrm{}}$ on the fraction of antiprotons expected in the cosmic-ray flux at the top of Earth's atmosphere due to collisions of primary cosmic rays with interstellar hydrogen. The implication of this result for experiments designed to detect the existence of antimatter in the universe is discussed. We have parametrized existing data on the $\overline{p}$ inclusive cross section from threshold to intersecting-storage-ring energies to obtain the result.