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The gamma gamma to gamma gamma process in the Standard and SUSY models at high energies

We study the helicity amplitudes of the process γγ\to γγat high energy, which in the standard and SUSY models first arise at the one-loop order. In the standard model (SM), the diagrams involve W and charged quark and lepton loops, while in SUSY we also have contributions from chargino, charged sfermion and Higgs loop diagrams. The SUSY contributions are most important in the region above the threshold for producing the supersymmetric partners; since there, they interfere most effectively with the primarily imaginary SM amplitudes. Simple expressions for the relevant 1-loop functions are given, which provide a direct overview of the behaviour of the helicity amplitudes in the whole parameter space at high energies. The various characteristics of a large set of observables are studied in detail.