Anomalous Pseudoscalar-Photon Vertex In and Out of Equilibrium

Abstract

The anomalous pseudoscalar-photon vertex is studied in real time in and out of equilibrium in a constituent quark model. The goal is to understand the in-medium modifications of this vertex, exploring the possibility of enhanced isospin breaking by electromagnetic effects as well as the formation of neutral pion condensates in a rapid chiral phase transition in peripheral, ultrarelativistic heavy-ion collisions. In equilibrium the effective vertex is afflicted by infrared and collinear singularities that require hard thermal loop (HTL) and width corrections of the quark propagator. The resummed effective equilibrium vertex vanishes near the chiral transition in the chiral limit. In a strongly out of equilibrium chiral phase transition we find that the chiral condensate drastically modifies the quark propagators and the effective vertex. The ensuing dynamics for the neutral pion results in a potential enhancement of isospin breaking and the formation of ${\pi }^0$ condensates. While the anomaly equation and the axial Ward identity are not modified by the medium in or out of equilibrium, the effective real-time pseudoscalar-photon vertex is sensitive to low energy physics.

Revised version to appear in Phys. Rev. D. 42 pages, 4 figures, uses Revtex

References in corpus (1)

• Non-equilibrium phase transitions in condensed matter and cosmology: spinodal decomposition, condensates and defects

Cited by in corpus (7)

• Production of ${\eta }^{\prime }$ from Thermal Gluon Fusion
• Neutral Pion Decay Width in a Hot and Dense Medium
• Nonequilibrium pion dynamics near the critical point in a constituent quark model
• Candidates for HyperCharge Axion in Extensions of the Standard Model
• Anomalous processes at high temperature and density in a 2-dimensional linear $\sigma$ model
• Out-of-equilibrium Photon Production from Disoriented Chiral Condensates
• Pion production in nonequilibrium Chiral perturbation Theory