Can Induced Theta Vacua be Created in Heavy Ion Collisions?

TL;DR

This paper explores the possibility of creating theta-vacua in heavy ion collisions, demonstrating through a simple model that non-zero theta states can form rapidly, which has implications for axion searches.

Contribution

It provides a numerical study showing that theta-vacua can be generated in heavy ion collisions within a simple two-flavor QCD model.

Findings

Non-zero theta-vacua can form in heavy ion collisions.

Formation time of theta-vacua is approximately 10^{-23} seconds.

Results have implications for axion search experiments at RHIC.

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 $\theta\neq 0$ 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.