Some aspects of the theory of heavy ion collisions.

We review the theoretical aspects relevant in the description of high-energy heavy ion collisions, with an emphasis on the learnings about the underlying quantum chromodynamics phenomena that have emerged from these collisions.

Pressure isotropization in high energy heavy ion collisions.

The early stages of high energy heavy ion collisions are studied in the color glass condensate framework, with a real-time classical lattice simulation. When increasing the coupling constant, we observe a rapid increase of the ratio of longitudinal to transverse pressure. The transient regime that precedes this behavior is of the order of 1 fm/c.

Quantitative study of the violation of kperpendicular factorization in hadroproduction of quarks at collider energies.

We demonstrate the violation of kperpendicular factorization for quark production in high energy hadronic collisions. This violation is quantified in the color glass condensate framework and studied as a function of the quark mass, the quark transverse momentum, and the saturation scale Q(s), which is a measure of large parton densities. At x values where parton densities are large but leading twist shadowing effects are still small, violations of kperpendicularkfactorization can be significant--especially for lighter quarks. At very small x, where leading twist shadowing is large, we show that violations of kperpendicular factorization are relatively weaker.