  We study the phenomenology of, and search techniques for, a class of "Hidden
Valleys." These models are characterized by low mass (well below a TeV) bound
states resulting from a confining gauge interaction in a hidden sector; the
states include a spin-one resonance that can decay to lepton pairs. Assuming
that the hidden sector communicates to the Standard Model (SM) through TeV
suppressed operators, taking into account the constraint from the $Z$ pole
physics at LEP, searches at Tevatron may be difficult in the particular class
of Hidden Valleys we consider, so that we concentrate on the searches at the
LHC. Hidden Valley events are characterized by high multiplicities of jets and
leptons in the final state. Depending on the scale of confinement in the hidden
sector, the events are typically more spherical, with lower thrust and higher
incidences of isolated leptons, than those from the SM background processes.
Most notably, high cluster invariant mass and very narrow, low mass resonances
in lepton pairs are the key observables to identify the signal. We use these
characteristics to develop a set of cuts to separate the Hidden Valley from SM,
and show that with these cuts LHC has a significant reach in the parameter
space. Our strategies are quite general and should apply well beyond the
particular class of models studied here.
