The $\gamma \gamma \to \gamma \gamma $ process in the standard and SUSY models at high energies

G.J. Gounaris; P.I. Porfyriadis; F.M. Renard

doi:doi:10.1007/s100529900079

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Particles and Fields

Eur. Phys. J. C 9, 673-686
DOI 10.1007/s100529900079

The $\gamma \gamma \to \gamma \gamma$ process in the standard and SUSY models at high energies

G.J. Gounaris¹ - P.I. Porfyriadis¹ - F.M. Renard²

¹ Department of Theoretical Physics, University of Thessaloniki, GR-54006, Thessaloniki, Greece
² Physique Mathématique et Théorique, UMR 5825 Université Montpellier II, F-34095 Montpellier Cedex 5, France

Received: 3 February 1999 / Pulished online: 30 June 1999

Abstract
We study the helicity amplitudes of the process $\gamma \gamma \to \gamma \gamma$ at 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, 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; there, they interfere most effectively with the primarily imaginary SM amplitudes. Simple expressions for the relevant one-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.