EPJ

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EPJ C - Particles and Fields
Particles and Fields

Eur. Phys. J. C 10, 499-513
DOI 10.1007/s100529900131

The $\gamma \gamma \to \gamma Z $ process at high energies and the search for virtual SUSY effects

G.J. Gounaris1 - J. Layssac2 - P.I. Porfyriadis1 - F.M. Renard2

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

Received: 26 April 1999 / Published online: 8 September 1999

Abstract
We study the helicity amplitudes and the observables of the process $\gamma \gamma \to \gamma Z $ at high energy. As in the case of the $\gamma \gamma \to \gamma\gamma$ process studied before, the relevant diagrams in the standard model (SM) involve W, charged-quark, and lepton loops, while in SUSY we also have contributions from charginos and charged-sfermion or Higgs-loop diagrams. Above 250 GeV, the dominant SM amplitudes are themselves dominated by the W loop, and as for $\gamma \gamma \to \gamma\gamma$, they are helicity conserving and almost purely imaginary. We discuss the complementary information provided by $\gamma \gamma \to \gamma Z $ for the identification of possible nonstandard effects. This process, together with $\gamma \gamma \to \gamma\gamma$, should provide very useful information on the nature of possible new physics particles, above the threshold of their direct production.

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