Can Induced Theta Vacua be Created in Heavy Ion Collisions?

Abstract

The development of the early Universe is a remarkable laboratory for the study of most nontrivial properties of particle physics. What is more remarkable is the fact that these phenomena at the QCD scale can be, in principle, experimentally tested in heavy ion collisions. We expect that, in general, an arbitrary theta-state would be created in the heavy ion collisions, similar to the creation of the disoriented chiral condensate with an arbitrary isospin direction. It should be a large domain with a wrong $θ\neq 0$ orientation. We test this idea numerically in a simple model where we study the evolution of the phases of the chiral condensates in QCD with two quark flavors with non-zero theta-parameter. We see the formation of a non-zero theta-vacuum with the formation time of the order of $10^{-23}$ seconds. This result will have important implications for a possible axion search experiment at RHIC.