Options and implications for ep experiments at HERA and beyond

At the ep collider HERA 920 GeV protons collide with 27.5 GeV electrons or positrons. Until the year 2000 a luminosity of ≈180 pb−1 has been delivered to the two experiments H1 and ZEUS. A further substantial step in luminosity is expected from an luminosity upgrade which has been performed at HERA in 2001. A fourfold increase of the instantaneous luminosity should enable the experiments H1 and ZEUS to collect ≈1 fb−1 until the end of 2006. Furthermore, the installation of spin rotators will allow studies of polarised e→p scattering. In order to fully exploit the upgraded machine extensive detector upgrades were performed emphasising enhanced trigger and tracking capabilities. Various possibilities for future lepton–hadron colliders based on existing facilities like HERA or RHIC are presently being discussed. They include options for polarised protons, deuterons and heavier nuclei as well as higher centre of mass energies of s⩾1 TeV.