Dynamics of an interacting hadron gas and measurements of Υ(nS) production and polarization in proton-proton collisions at √s = 13.6 TeV with ALICE

Abstract

Ultra-relativistic heavy-ion collision programs at the Large Hadron Collider (LHC) at CERN and the Relativistic Heavy Ion Collider (RHIC) at BNL are designed to explore strongly interacting matter under extreme conditions of temperature and energy density. In these experiments, the so-called little Bang created in ultra-relativistic nuclear collisions leads to the formation of a novel state of matter known as the quark–gluon plasma (QGP), in which quarks and gluons are no longer confined within hadrons. This state of matter is believed to have existed during the first few microseconds after the Big Bang. Consequently, studying the properties of QGP not only deepens our understanding of the strong interaction at the microscopic level but also provides valuable insight into the early evolution of the universe. The short lifetime of the QGP matter does not leave any direct signature. Its properties are inferred through indirect signatures and through a detailed understanding of the system’s evolution across different stages of the space-time evolution of the created fireball. The transport properties can play a major role in characterizing the dynamical evolution of the produced medium. Since the transport coefficients can, in principle, be derived from fundamental theory, their variation with thermodynamic parameters such as temperature and chemical potential can be useful in identifying the phase structure of QCD.