  We present a study of a class of effective actions which show typical
axion-like interactions, and of their possible effects at the Large Hadron
Collider. One important feature of these models is the presence of one
pseudoscalar which is a generalization of the Peccei-Quinn axion. This can be
very light and very weakly coupled, with a mass which is unrelated to its
couplings to the gauge fields, described by Wess Zumino interactions.
  We discuss two independent realizations of these models, one derived from the
theory of intersecting branes and the second one obtained by decoupling one
chiral fermion per generation (one right-handed neutrino) from an anomaly-free
mother theory. The key features of this second realization are illustrated
using a simple example.
  Charge assignments of intersecting branes can be easily reproduced by the
chiral decoupling approach, which remains more general at the level of the
solution of its anomaly equations. Using considerations based on its lifetime,
we show that in brane models the axion can be dark matter only if its mass is
ultralight ($\sim 10^{-4}$ eV), while in the case of fermion decoupling it can
reach the GeV region, due to the absence of fermion couplings between the heavy
Higgs and the light fermion spectrum. For a GeV axion derived from brane models
we present a detailed discussion of its production rates at the LHC.
