Near-threshold production of the multi-strange $Xi^-$ hyperon

The yield for the multi-strange $Xi^{-}$ hyperon has been measured in 6 AGeV Au+Au collisions via reconstruction of its decay products $pi^{-}$ and $Lambda$, the latter also being reconstructed from its daughter tracks of $pi^{-}$ and p. The measurement is rather close to the threshold for $Xi^{-}$ production and therefore provides an important test of model predictions. The measured yield for $Xi^{-}$ and $Lambda$ are compared for several centralities. In central collisions the $Xi^{-}$ yield is found to be in excellent agreement with statistical and transport model predictions, suggesting that multi-strange hadron production approaches chemical equilibrium in high baryon density nuclear matter.