Aspects of relativistic heavy-ion collisions

The rapid thermalization of quarks and gluons in the initial stages of relativistic heavy-ion collisions is treated using analytic solutions of a nonlinear diffusion equation with schematic initial conditions, and for gluons with boundary conditions at the singularity. On a similarly short time scale of $t \le1$ fm/$c$, the stopping of baryons is accounted for through a QCD-inspired approach based on the parton distribution functions of valence quarks, and gluons. Charged-hadron production is considered phenomenologically using a linear relativistic diffusion model with two fragmentation sources, and a central gluonic source that rises with $\ln^3(s_{NN})$. The limiting-fragmentation conjecture that agrees with data at energies reached at the Relativistic Heavy Ion Collider (RHIC) is found to be consistent with Large Hadron Collider (LHC) data for Pb-Pb at $\sqrt{s_{NN}}= 2.76$ and $5.02$ TeV. Quarkonia are used as hard probes for the properties of the quark-gluon plasma (QGP) through a comparison of theoretical predictions with recent CMS, ALICE and LHCb data for Pb-Pb and p-Pb collisions.