The name "hidden valley" models was coined in 2006 by Strassler and Zurek
and the paper above, references 1-6, show you the origin of these papers; 6 are stringy constructions. The models may be supersymmetric but they don't have to be. The "valley" refers to some place in the hidden dimensions of spacetime where an additional gauge group $G$ added as a factor to the Standard Model is localized. The new states are uncharged under the Standard Model and only charged under the new gauge group.
The new gauge group and the new particles/fields charged under the new group are ad hoc from the field theory viewpoint and there is no minimal choice. On the other hand, such new gauge groups and states are natural in string theory so it makes to study and realize what consequences such hypothetical states would have.
This post imported from StackExchange Physics at 2014-03-12 15:30 (UCT), posted by SE-user Luboš Motl