TLEP has enormous potential for accurate Higgs measurements, as well as measurements of unprecedented precision at the Z peak and the WW threshold. Its physics programme can pave the way towards the discovery of physics beyond the standard model by testing the closure of the standard model with a precision not available at other machines. It is an ambitious project which nevertheless relies on the evolution of proven technology. LEP3 is a much more modest project which however has a much lower cost due to extensive use of the existing LHC infrastructure, including the two main experiments ATLAS and CMS. It can start after the completion of the LHC programme.
Our initial studies show that circular colliders of this size offer a series of advantages over linear machines: Higher luminosity, better reliability, many interaction points, a richer electroweak programme, better experimental environment, and lower cost. No showstoppers have been identified. Since such machines would be "burning up" beams so efficiently (beam lifetimes due to physics processes is a few minutes) a top-up scheme is envisaged (above right)
We consider the concept to be highly interesting and deserving a detailed study. Depending on what is discovered at the LHC when it runs close to its design energy, LEP3/TLEP might provide a very attractive alternative to other projects for the medium term (twenties to thirties).