U(A)(1) Anomaly in Hot and Dense QCD and the Critical Surface
Journal
Physics Review
Journal Volume
D80
Pages
054012
Date Issued
2009-02
Author(s)
Abstract
We discuss the chiral phase transition in hot and dense QCD with three light flavors. Inspired by the well-known fact that the UA(1) anomaly could induce first order phase transitions, we study the effect of the possible restoration of the UA(1) symmetry at finite density. In particular, we explore the link between the UA(1) restoration and the recent lattice QCD results of de Forcrand and Philipsen, in which the first order phase transition region near zero chemical potential (μ) shrinks in the quark mass and μ space when μ is increased. Starting from the Ginzburg-Landau theory for general discussions, we then use the Nambu-Jona-Lasinio model for quantitative studies. With the partial UA(1) restoration modeled by the density dependent 't Hooft interaction, we fit the shrinking of the first order region found in de Forcrand and Philipsen's lattice calculation at low μ. At higher μ, the first order region might shrink or expand, depending on the scenarios. This raises the possibility that despite the shrinking of the first order region at lower μ, the QCD critical end point might still exist due to the expansion at higher μ. In this case, very high precision lattice data will be needed to detect the recently observed backbending of the critical surface with the currently available analytic continuation or Taylor expansion approaches. Lattice computations could, however, test whether the UA(1) restoration is responsible for the shrinking of the first order region by computing the η′ mass or the topological susceptibility at small μ. © 2009 The American Physical Society.
Type
journal article