CERN Accelerating science

A strongly interacting state of matter known as the Quark-Gluon Plasma (QGP) is formed in the high temperature and high energy density conditions reached in ultra-relativistic heavy-ion collisions, such as the Pb–Pb collisions measured at the Large Hadron Collider (LHC). One of the key measurements for the understanding of the properties of the QGP medium created in these collisions is the production of strange and multi-strange hadrons. ALICE is one of the four major experiments of the LHC and has a detector designed to study identified particle production rates from heavy-ion collisions. The excellent tracking and particle identification capabilities allow the reconstruction of multi-strange baryons ($\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$ and $\bar{\Omega}^{+}$) via their weak decay channels over a large range in transverse momentum ($p_{\rm T}$). In this thesis, we study the multi-strange particle production at central rapidity Pb–Pb collisions measured by ALICE at the unprecedented energy of $\sqrt{s_{NN}} = 5.02$ TeV and $2.76$ TeV. The yields are normalized by the corresponding measurement of pion production in the same centrality class in order to study the strangeness enhancement, effect predicted as a probe of the QGP. Comparison of hyperon-to-pion ratio between different systems, such as pp, p–pb and Pb–Pb collisions, shows that production of multi-strange baryons relative to pions follows a continuously increasing trend from low multiplicity pp to central Pb–Pb collisions.