  The Lagrangian of non-Abelian tensor gauge fields describes the interaction
of the Yang-Mills and massless tensor bosons of increasing helicities. We have
found a metric-independent gauge invariant density which is a four-dimensional
analog of the Chern-Simons density. The Lagrangian augmented by this
Chern-Simons-like invariant describes massive Yang-Mills boson, providing a
gauge-invariant mass gap for a four-dimensional gauge field theory. We present
invariant densities which can provide masses to the high rank tensor bosons.
