High-Energy Frontier Circular Colliders

Starting from the LHC experience in 2010-12, I review the LHC plan for the next ten years, followed by a presentation of the HL-LHC project. Next, the combination of LHeC (ep) and SAPPHiRE (gamma-gamma) is discussed as a pair of intermediate Higgs factories, which could be run in parallel to the HL-LHC, and which would provide the RF system and injector complex for a later e+e- Higgs factory. Possible future higher-energy hadron colliders include HE-LHC and VHE-LHC. The 80-100 km tunnel built for the latter could also host a circular e+e- Higgs factory, TLEP, offering high resolution for many of the Higgs coupling parameters, with sensitivity to new physics at multi-TeV energies. Finally I propose a long-term strategy based on a sequence of circular high-energy colliders, including possible steps beyond VHE-LHC and ultimate limitations. Presented at the KEK Accelerator Seminar, 23 July 2013.