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UBC Theses and Dissertations

Induced theta vacua in heavy ion collisions Buckley, Kirk B. W.


In the following we demonstrate that it is possible to create non-zero θ-states during heavy ion collisions. Using the effective Lagrangian for low energy QCD derived in [1, 2], we will show numerically that in the period immediately following a quench, the chiral condensate phases fa and fa will relax to the value ~ θ /N[sub f]. This is a true condensate in the sense that if the volume of the system is changed, the zero mode still remains. If such a state can be created, it would decay by various mechanisms to the θ[sup fund] = 0 state which exists in our world. We will discuss the experimental signature for the produced non-trivial θ-state. In particular, we will provide evidence that the creation of a non-zero θ -state would result in an excess of low momentum particles (π⁰, ƞ, and ƞ'-mesons) , in the (10 - 100) MeV range. This phenomena could possibly account for the excess of low momentum dileptons observed at CERN [3, 4].

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