CERN Accelerating science

The Large Hadron Collider (LHC) at CERN, Geneva, Switzerland, stands at the forefront of our current understanding of high energy physics. Several important measurements, including assisting in the discovery of the Quark Gluon Plasma (QGP), have been made in recent years thanks to the efforts of the LHC. Further study of the properties of matter in these systems proves to be instrumental in our understanding of the universe and the physics used to describe it. Recent lattice quantum chromo dynamic (QCD) calculations seem to indicate the phenomenon of chiral symmetry restoration, which would result in changes in the masses of some hadron species under extreme conditions of pressure and temperature. These lattice QCD calculations highlight the idea of parity doubling, where the masses of negative parity particles decrease when the system approaches a pseudo-critical temperature and phase transition. Investigation into the modification of the affected particle's mass, width, and yield due to partial chiral symmetry restoration would prove instrumental to confirming some of the last remaining predictions of QCD. Measurements of the $\Xi$(1820)$^{-}$ and its antiparticle were performed with the ALICE detector in p-p, p-Pb, and Pb-Pb collisions at LHC energies $\sqrt{s}$ = 13 TeV for p-p and $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV for p-Pb and Pb-Pb. The mass, width, and yield of $\Xi$(1820) are obtained and compared in various collision systems. The yield ratios of $\Xi$(1820) to $\Xi$(1530) and $\Xi$ are shown and discussed. Analysis into the $\Xi$(1820)$^{\mp}$ in p-p, p-Pb, and Pb-Pb collisions at LHC shows several signatures of chiral symmetry restoration. Most notably, a 2.38 $\sigma$ difference between the width of $\Xi$(1820)$^{\mp}$ signals from minimum bias p-p $\sqrt{s}$ = 13 TeV and central Pb-Pb $\sqrt{s_{NN}}$ = 5.02 TeV data is observed. While very impressive, more statistics are required to reach a conclusive statement.