Search

We develop a far-from-equilibrium hydrodynamic model to evolve ultrarelativistic heavy-ion collisions in event-by-event simulations. Anisotropic hydrodynamics is designed to better handle the strong and highly anisotropic expansion during the early stages of the collision. The large gradients cause conventional second-order viscous hydrodynamic approaches to break down at early times. Anisotropic hydrodynamics evolves the large pressure anisotropies present in the quark-gluon plasma non-perturbatively, which prevents negative longitudinal pressures from developing even under extreme conditions. This increased stability allows us to start anisotropic hydrodynamics already at a very early longitudinal proper time to evolve the pre-hydrodynamic stage. In current pre-hydrodynamic models, the equation of state is not consistent with the QCD equation of state used in the subsequent fluid dynamic stage. Since our approach avoids this inconsistency, we are able to achieve a smooth transition to non-conformal viscous hydrodynamics as the gradients decrease over time. For our first phenomenological application, we apply our new simulation to model fluctuating Pb+Pb collisions at LHC energies ($\sqrt{s_\text{NN}} = 2.76$ TeV) and find that our preliminary calculations for the hadronic observables are in excellent agreement with the experimental data., Comment: PhD thesis, 332 pages

The iS3D particlization module simulates the emission of hadrons from heavy-ion collisions via Monte-Carlo sampling of the Cooper-Frye formula which converts fluid dynamical information into local phase-space distributions for hadrons. The code package includes multiple choices for the non-equilibrium correction to these distribution functions: the 14-moment approximation, first-order Chapman-Enskog expansion, and two types of modified equilibrium distributions. This makes it possible to explore to what extent heavy-ion experimental data are sensitive to different choices for $\delta f_n$, presently the main source of theoretical uncertainty in the particlization stage. We validate our particle sampler with a high degree of precision by generating several million hadron emission events from a longitudinally boost-invariant hypersurface and comparing the event-averaged particle spectra and space-time distributions to the Cooper-Frye formula.