2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 13, 79-97
DOI 10.1007/s100520000307

The $\gamma \gamma \to Z Z $ process and the search for virtual SUSY effects at a $\gamma \gamma $ Collider

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

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

Received: 3 September 1999 / Published online: 3 February 2000 - © Springer-Verlag 2000

Abstract
We study the helicity amplitudes of the process $\gamma \gamma \to Z Z $ in the Standard Model at high energy. These amplitudes receive contributions from the W and charged quark and lepton loops, analogous to those encountered in the $\gamma \gamma \to \gamma\gamma, ~\gamma Z$ cases studied before. But $\gamma \gamma \to Z Z $ also receives contributions from the Higgs s-channel poles involving the effective Higgs- $\gamma \gamma $ vertex. At energies $\gtrsim300 GeV$, the amplitudes in all three processes are mainly helicity-conserving and almost purely imaginary; which renders them a very useful tool in searching for New Physics. As an example, a SUSY case is studied, and the signatures due to the virtual effects induced by a chargino-, charged slepton- or a lightest stop-loop in $\gamma \gamma \to Z Z $, are explored. These signatures, combined with the analogous ones in $\gamma \gamma \to \gamma \gamma$and $\gamma \gamma \to \gamma Z$, should help identifying the nature of possible New Physics particles.


Copyright Società Italiana di Fisica, Springer-Verlag 2000