Inclusive and semi-inclusive measurements are presented for antiproton (p̄) production in proton-nucleus collisions at the Alternating Gradient Synchrotron (AGS). The inclusive yields per event increase strongly with increasing beam energy and decrease slightly with increasing target mass. The p̄ yield in 17.5 GeV/c p + Au collisions decreases with grey track multiplicity, Ng, for Ng>0, consistent with annihilation within the target nucleus. The relationship between Ng and the number of scatterings of the proton in the nucleus is used to estimate the p̄ annihilation cross section in the nuclear medium. The resulting cross section is at least a factor of 5 smaller than the free p̄-p annihilation cross section when assuming a small or negligible formation time. Only with a long formation time can the data be described with the free p̄-p annihilation cross section.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics