Stuckelberg Axions and the Effective Action of Anomalous Abelian Models 2. A SU(3)_C x SU(2)_W x U(1)_Y x U(1)_B model and its signature at the LHC

Abstract

We elaborate on an extension of the Standard Model with a gauge structure enlarged by a single anomalous U(1), where the presence of a Wess-Zumino term is motivated by the Green-Schwarz mechanism of string theory. The additional gauge interaction is anomalous and requires an axion for anomaly cancelation. The pseudoscalar implements the St\"{u}ckelberg mechanism and undergoes mixing with the standard Higgs sector to render the additional U(1) massive. We consider a 2-Higgs doublet model. We show that the anomalous effective vertices involving neutral currents are potentially observable. We clarify their role in the case of simple processes such as $Z^*\to \gamma \gamma$, which are at variance with respect to the Standard Model. A brief discussion of the implications of these studies for the LHC is included.