  String theory constructions using D-brane physics offer a framework where
ingredients like extra abelian factors in the gauge group, more than one Higgs
doublet and a generalized Green-Schwarz mechanism appear at the same time.
Motivated by works towards the direction of obtaining the Standard Model in
orientifold constructions, we study in the present work a Stueckelberg
extension of the two-Higgs-doublet model. The distinctive features of our model
are i) a sharp decay width for the heavy gauge boson, and ii) a charged Higgs
boson having two main decay channels at tree level with equal branching ratios.
