  We obtain the light meson mass spectroscopy from the light-front quantum
chromodynamics (QCD) Hamiltonian, determined for their constituent
quark-antiquark and quark-antiquark-gluon Fock components, together with a
three-dimensional confinement. The eigenvectors of the light-front effective
Hamiltonian provide a good quality description of the pion electromagnetic form
factor, decay constant, and the valence quark distribution functions following
QCD scale evolution. We also show that the pion's gluon densities can be probed
through the pion-nucleus induced $J/\psi$ production data. Our pion parton
distribution functions provide excellent agreement with $J/\psi$ production
data from widely different experimental conditions.
