LHC Luminosity and energy upgrade: A Feasibility Study

We discuss a possible staged upgrade of the LHC and of its injectors, with a view to increasing the luminosity from the nominal 10**34 cm**-2s**-1 to 10**35 cm**-2s**-1 in each of the two high-luminosity experiments. We also consider possible scenarios for an upgrade to a proton beam energy of about 14 TeV. Starting from beam dynamics considerations and fundamental limitations of the hardware subsystems, we derive realistic requirements for the major components, such as superconducting magnets, cryogenic and RF systems, beam dump and vacuum. We also discuss a novel approach to the optimization of the collider performance, compatible with the beam-beam limit for high intensity proton bunches or long "super-bunches", and sketch a new design of the interaction regions, including an alternative beam crossing scheme. Finally we identify further studies required for an LHC performance upgrade and propose an R&D programme