PHYSICS WITH E(+)E(-) LINEAR COLLIDERS

The physics potential of e(+) e(-) linear colliders is summarized in t his report. These machines are planned to operate in the first phase a t a center-of-mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision test s of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the proper ties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theori es can be searched for and studied thoroughly. The machines provide un ique opportunities for the discovery of particles in supersymmetric ex tensions of the Standard Model, the spectrum of Higgs particles, the s upersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties a nd interactions will allow for extrapolations to energy scales close t o the Planck scale where gravity becomes significant. In alternative s cenarios, i.e. compositeness models, novel matter particles and intera ctions can be discovered and investigated in the energy range above th e existing colliders lip to the TeV scale. Whatever scenario is realiz ed in Nature, the discovery potential of e(+) e(-) linear colliders an d the high precision with which the properties of particles and their interactions can be analyzed, define an exciting physics program compl ementary to hadron machines. (C) 1998 Elsevier Science B.V. All rights reserved.