CERN Accelerating science

This thesis aims to shed light on key aspects of quantum chromodynamics (QCD) by examining recent studies carried out at the Large Hadron Collider (LHC) at CERN. The research focuses on understanding the transport properties of matter created in heavy-ion collisions, specifically the specific shear and bulk viscosity, which provide essential information about QCD. Three primary goals steer this investigation. The first goal is to accurately estimate these transport properties based on experimental data. This is achieved through the use of Bayesian analysis and additional flow observables that predominantly reflect non-linear hydrodynamic responses. Despite existing uncertainties in model calculations, this approach has shown to reduce these uncertainties significantly. The second goal is to conduct higher-order multiparticle correlation measurements. Bayesian analysis has allowed for the quantification of the sensitivities of each observable, and it has been found that observables reflecting a hydrodynamic nonlinear response are most sensitive to the transport properties. Lastly, the third goal is to explore the formation of the Quark-Gluon Plasma (QGP). The thesis investigates the smallest system size necessary for the formation of QGP and also probes whether small and large collision systems exhibit the same underlying mechanism for similar observations. In summary, this thesis explores the depths of QCD, with the aim of enhancing understanding and reducing uncertainties of the QCD matter properties through precise measurements and analysis.