  It is possible that the standard model is coupled, through new massive
charged or colored particles, to a hidden sector whose low energy dynamics is
controlled by a pure Yang-Mills theory, with no light matter. Such a sector
would have numerous metastable "hidden glueballs" built from the hidden gluons.
These states would decay to particles of the standard model. We consider the
phenomenology of this scenario, and find formulas for the lifetimes and
branching ratios of the most important of these states. The dominant decays are
to two standard model gauge bosons, or by radiative decays with photon
emission, leading to jet- and photon-rich signals.
