CERN Accelerating science

In the Standard Model of particle physics, Quantum Chromodynamics (QCD) is the theory describing the strong interaction among quarks and gluons. Under extreme conditions of temperature and/or pressure, QCD predicts a phase transition from ordinary matter to the so-called Quark-Gluon Plasma (QGP), in which quarks and gluons are deconfined. QGP can be created at accelerators, like the Large Hadron Collider at CERN, by colliding heavy-ion at ultra-relativistic speed. Due to its short lifetime, the QGP can- not be observed directly and, therefore, the investigation of its properties proceeds by means of probes. The idea is that quarks interact with the hot and dense medium losing energy in the process and acquiring collective features. Afterward, once the plasma cools down below a certain temperature, they dress to form hadrons. By investigating the properties of those hadrons with respect to reference properties evaluated in a system where QGP is not created, it is possible to infer information on the plasma thermodynamical and transport properties. A well-established experimental observable is the so-called nuclear modification factor. It is based on the comparison of the yield of particles produced in heavy-ion collisions to a reference evaluated in proton-proton collisions. In this thesis dissertation, we will discuss recent measurements of the D$^{\ast +}$-meson production in lead-lead collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV and relative nuclear modification factor. In addition, the detailed comparison with theoretical models will be discussed.