Multi-nucleon mechanism for subthreshold antiproton production in proton-nucleus reactions

We study a many-body (multipion) mechanism for -p subthreshold production in proton-nucleus collisions. The incoming proton and the interacting nucleons in the target act as sources of pions that merge to produce a nucleon-antiproton pair. The calculation takes fully into account the initial state interaction and antiproton absorption in the final state. The cooperation of several nucleons in the initial state reduces the threshold for the reaction allowing for production rates that may account for 15-50% of the total -p production. We point out that this contribution should be added to the primary -p production mechanism due to Δ formation and rescattering, as found by other groups, and should be taken into account when trying to extract information about -p properties in the nuclear medium.