Multi-strange baryon production at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV

The ALICE experiment at the LHC has measured the production of $\Xi^-$ and $\Omega^-$ baryons and their anti-particles in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The transverse momentum spectra at mid-rapidity (|y| < 0.5) for charged $\Xi$ and $\Omega$ hyperons have been studied in the range 0.6 < $p_T$ < 8.0 GeV/c and 1.2 < $p_T$ < 7.0 GeV/c, respectively, and in several centrality intervals (from the most central 0-10% to the most peripheral 60-80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, the Kraków and EPOS models give a satisfactory description of the data, with the latter covering a wider $p_T$ range. Mid-rapidity yields, integrated over $p_T$, have been determined. The hyperon-to-pion ratios are similar to those at RHIC: they rise smoothly with centrality up to $<N_{part}>$ ~ 150 and saturate thereafter. The enhancements (yields per participant nucleon relative to p-p collisions) increase both with the strangeness content of the baryon and with centrality, but are less pronounced than at lower energies.