Axions and Anomaly-Mediated Interactions: The Green-Schwarz and   Wess-Zumino Vertices at Higher Orders and g-2 of the muon
  We present a study of the mechanism of anomaly cancellation using only transverse invariant amplitudes on anomaly diagrams at higher perturbative orders. The method is the realization of the Green-Schwarz (GS) mechanism at field theory level, which restores the Ward identities by a subtraction of the anomaly pole. Some of the properties of the GS vertex are analyzed both in the context of unitarity and of the organization of the related perturbative expansion. We investigate the role played by the GS and the Wess-Zumino vertices in the anomalous magnetic moment of the muon and in the hyperfine splitting of muonium, which are processes that can be accompanied by the exchange of a virtual anomalous extra Z-prime and an axion-like particle. 
Roberta Armillis, Claudio Coriano', Marco Guzzi and Simone Morelli