Figure 2

Acceptance $\times$ efficiency factors for $\rm\Xi^{-}$ (circles) and $\rm\Omega^{-}$ (squares) at mid-rapidity as a function of $\pt$, both for the most central 0-10% (full symbols) and the most peripheral 60-80% (open symbols) Pb-Pb collisions. The points already take into account the branching ratios of the corresponding measured decay channels. Those for the $\rm\Omega^{-}$ are also scaled by a factor of 0.75, to avoid overlap with the $\rm\Xi^{-}$ at high $\pt$.