  High energy hadron colliders have been the tools for discovery at the highest
mass scales of the energy frontier from the SppS, to the Tevatron and now the
LHC. This report reviews future hadron collider projects from the high
luminosity LHC upgrade to a 100 TeV hadron collider in a large tunnel, the
underlying technology challenges and R&D directions and presents a series of
recommendations for the future development of hadron collider research and
technology.
