${\barΛ}/{\bar p}$ ratios in heavy ion collisions at 11.6 AGeV/c

Abstract

We attempt to explain the ${\bar Λ}/\bar p$ ratios measured in heavy ion collisions at $11.6~{\rm A\cdot GeV}/c$ beam momentum within a hadronic framework. This ratio is enhanced relative to corresponding ratios in $pp$ collisions, and is large when compared with thermal fits to heavy ion data. Using a detailed cascade calculation, we show that different annihilation cross--sections of $\bar Λ$'s and $\bar p$'s, and the net conversion of $\bar p$'s to $\bar Λ$'s, do not account for the enhancement in central collisions. For larger impact parameters, however, hadronic mechanisms may well suffice to produce the observed enhancement. Uncertainties in elementary cross--sections and formation times are considered.