Anti-Lambda/Anti-Proton ratios at the AGS

Abstract

We attempt to explain the large ${\bar \Lambda}/\bar p$ ratios measured in heavy ion collisions at $12~{\rm A\cdot GeV}/c$ beam momentum within an hadronic framework. The ratios are large compared to corresponding ratios in $pp$ collisions, and to thermal fits. We show using a simple model and a detailed cascade calculation that different annihilation cross--sections of $\bar \Lambda$'s and $\bar p$'s, and the net conversion of $\bar p$'s to $\bar \Lambda$'s, do not account for the enhancement. Uncertainties in elementary cross--sections and formation times are also considered.