Soutenance de thèse

vendredi 30 septembre 2022 à 14:30


The Beam Energy Scan under the scope of EPOS 4 - Studying the impact of hadronic cascades on the 2nd order cumulants of conserved net-charges in heavy-ion collisions

Johannès Jahan

Subatech, équipe Théorie

During the last two decades, heavy-ion collisions at ultra-relativistic energies have been used to investigate the properties of the Quark-Gluon Plasma (QGP), a state of matter in which quarks & gluons are deconfined from hadrons. One of the major goals of this research is to map the phase diagram of nuclear matter, made possible experimentally thanks to the Beam Energy Scan (BES) program. It is performed, among other objectives, to search for a 1st order phase transition and a critical endpoint between QGP and hadron gas phases. Ratios of net-multiplicities cumulants has been shown to be relevant experimental proxies for such study, due to their link with thermodynamic susceptibilities. In this regard, the STAR collaboration has recently published measurements of the 2nd order cumulants of net-multiplicities for pions, kaons and protons in Au+Au collisions at several energies of the BES program. However, signatures from a 1st order transition or a critical point may be blurred out by the last stages of the collision. Taking advantage of the modular conception of the EPOS event generator, the impact of the hadronic cascades on these 2nd order cumulants has been studied. The STAR proxies results are also compared with the 2nd order cumulants of the corresponding conserved charges, and with enhanced proxies proposed by the authors of a study based on lattice quantum chromodynamics calculations and the use of a Hadron Resonance Gas model. This work takes place in the context of developments for a new version of EPOS, what requires to validate its reliability by comparing simulations with experimental data for a wide range of systems and beam energies. The integration of the RIVET analysis toolkit, which has been achieved to facilitate this validation process, is also presented in this thesis.