Prospects for multi-TeV two-beam linear colliders

Recent work at CERN and SLAC has opened the possibility of the development of concrete designs for electron positron linear colliders that have a center of mass energy substantially above 1 TeV. These designs are based on high gradient, normal conducting acceleration with the power provided by an auxiliary beam that is efficiently accelerated in a fully loaded, low frequency linac. This type of power source offers a flexibility to develop linear collider designs that have a wide range of parameters. In particular, the choice of frequency can be made without regard to the availability of high power RF sources, at least up to about 30 GHz. This paper explores possible linear collider designs taking into account limits on acceleration gradient and beam-beam effects. The study shows that electron positron linear colliders have an energy reach far in excess of 1 TeV. In particular we show that an X-band linear collider powered with conventional sources might be upgraded using two-beam techniques to an energy far above 1 TeV. Thus, the linear collider offers a platform for continued exploration at the energy frontier of High Energy Physics