Ozonder, Sener2013-10-252013-10-252013-08https://hdl.handle.net/11299/159046University of Minnesota Ph.D. dissertation. August 2013. Major: Physics. Advisor: Joseph I. Kapusta. 1 computer file (PDF); xii, 86 pages, appendices A-E.In the ultrarelativistic heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC), Brookhaven National Lab (BNL) and the Large Hadron Collider (LHC), CERN, hot, dense and strongly interacting Quark Gluon Plasma has been created. After the Quark Gluon Plasma reaches local thermal equilibrium, the fireball expands rapidly. Relativistic hydrodynamics successfully captures this evolution given the initial energy and initial entropy densities, along with the equation of state. This is followed by freeze-out of the plasma into hadrons, which are finally recorded at the detectors. The final multiplicity of the detected particles as well as their distribution in transverse momentum and rapidity are determined by the initial conditions of the hydrodynamic evolution of the Quark Gluon Plasma. In this thesis, the initial energy density of heavy-ion collisions is calculated in the framework of an effective model based on Quantum Chromodynamics. An overview of heavy ion collisions and Quark Gluon Plasma is given first. Then, the three-dimensional, color neutral McLerran-Venugopalan model is introduced and its parameters are fixed from the data on gluon distribution functions. Finally, we apply this model to Au-Au (at RHIC) and Pb-Pb (at LHC) collisions to calculate the initial energy density. The most important result of the work presented here is calculation of the rapidity profile of the initial energy density. Finally we compare our results on the energy density profile with that is used in hydrodynamic simulations.en-USColor Glass CondensataInitial ConditionsMcLerran-VenugopalanQuark Gluon PlasmaRapidityRHICThesis or Dissertation