PUB - Publikationen an der Universität Bielefeld

We investigate the out-of-equilibrium dynamics of heavy-ion collisions by performing real-time lattice simulations, accompanied by analytical considerations within the framework of the Color Glass Condensate (CGC) effective theory of QCD. The central aim of this work is to relax the assumption of boost invariance and to gain insights into the longitudinal structure of the fireball.

In the first main part of the thesis, we simulate the 3+1 D classical Yang-Mills dynamics of the collisions of longitudinally extended nuclei, described by eikonal color charges in the CGC framework. By varying the longitudinal thickness of the colliding nuclei, we discuss the violations of boost invariance and explore how the boost invariant high-energy limit is approached. Subsequently, we develop a more realistic model of the 3~D color charge distributions, and explore the rapidity profiles and the longitudinal fluctuations that emerges naturally within our framework.

In the second main part, we perform an analytic calculation of the color fields in heavy-ion collisions, by considering the collision of extended nuclei in the dilute limit of the Color Glass Condensate effective field theory of high-energy QCD. Based on general analytic expressions for the color fields in the forward light cone, we evaluate the rapidity profile of the transverse pressure within a simple specific model of the nuclear collision geometry and compare our results to 3+1D classical Yang-Mills simulations.

In the third part of this thesis, we study the rapidity dependence of initial state momentum correlations and event-by-event geometry in p+Pb collisions at LHC energies $(\sqrt{s}=5.02~\rm{TeV})$ within the 3+1~D IP-Glasma model. We find that the event geometry is correlated across large rapidity intervals whereas initial state momentum correlations are relatively short range in rapidity. Based on our results, we discuss implications for the relevance of both effects in explaining the origin of collective phenomena in small systems.