Effects of Charge Density on the Geometry of Proton-Proton and Nucleus-Nucleus Collisions

Relativistic viscous hydrodynamics has been tremendously successful in describing the soft sector of heavy-ion collisions. The initial conditions have traditionally specified the energy density, but more recent models have included the effects of initial flow and initial shear stress. Recent breakthroughs have extended this paradigm to the charge sector as well. Modern hydrodynamic simulations have now confirmed that charge anisotropies in the initial state survive to influence the net anisotropic flow of charged particles in the final state. In this work, we study the effects of various initial charge density scenarios on the initial-state geometry of proton-proton and nucleus-nucleus collisions. We show both that an isotropic charge density can reduce the overall eccentricity due to the energy density, and that an anisotropic charge density can generate anisotropy from an isotropic energy density. To investigate these effects in heavy-ion collisions, we modify the open-source initial-state Trento model to compute initial charge geometries.