COSMIC-RAY SECONDARY ANTIPROTONS - A CLOSER LOOK

Following a suggestion of Webber that early calculations underestimated the intensity of secondary antiprotons, we have systematically reexamined three aspects of the calculation: the normalization and shape of the present interstellar spectrum, nuclear enhancement of antiproton production in collisions involving nuclei, and the mean energy-dependent residence time of secondary nuclei and antiprotons in the Galaxy. In particular, we have a new estimate of the nuclear enhancement factor, based on the wounded nucleon model. Here we find that the presence of heavy nuclei in the cosmic rays increases the antiproton flux by only 20% over a pure proton composition. We conclude that the reported experimental values of the antiproton-to-proton ratio of E(p) approximately 6-12 GeV remain significantly above the range of theoretical expectation allowed by uncertainties in the input assumptions.