3-D structure of the Glasma initial state: Breaking boost-invariance by collisions of extended shock waves in classical Yang-Mills theory

We simulate the 3+1 D classical Yang-Mills dynamics of the collisions of longitudinally extended nuclei, described by eikonal color charges in the Color Glass Condensate 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 three dimensional color charge distributions that connects longitudinal and transverse fluctuations to the $x$ and $k_T$ dependence of transverse momentum dependent parton distributions, and explore the resulting rapidity profiles and their longitudinal fluctuations.