arXiv:hep-ph/0203254v1 27 Mar 2002 PM/02-08 March 2002 The Reality of Virtual Supersymmetry † M. Beccaria a,b , F.M. Renard c and C. Verzegnassi d,e a Dipartimento di Fisica, Universit`a di Lecce, Via Arnesano, 73100 Lecce, Italy. b INFN, Sezione di Lecce c Physique Math´ematique et Th´eorique, UMR 5825 Universit´e Montpellier II, F-34095 Montpellier Cedex 5. d Dipartimento di Fisica Teorica, Universit`a di Trieste, Strada Costiera 14, Miramare (Trieste) e INFN, Sezione di Trieste Abstract We consider the high energy behaviour of the amplitudes for production of leptons, quarks, Higgs bosons, sleptons, squarks, gauge bosons, charginos and neutralinos at lep- ton colliders. We concentrate our discussion on the universal (process independent) log- arithmic terms which factorize the Born amplitude and which are typically of the form [a ln s m 2 - ln 2 s m 2 ]. We perform a systematic determination of the coefficient a for the various final states and we emphasize the striking features which differentiate the SM and the MSSM cases. We show that a comparison with experiments at future colliders should provide a clean way to test the gauge and Higgs structures of the electroweak interactions owing to the presence of sizable (visible) virtual logarithmic supersymmetric contributions. † Partially supported by EU contract HPRN-CT-2000-00149