Eur. Phys. J. C (2006) 46: 93-105
https://doi.org/10.1140/epjc/s2006-02474-1

Theoretical Physics

Effective-Lagrangian approach to γγ→WW II: Results and comparison with e⁺e^-→WW

Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120, Heidelberg, Germany

^* e-mail: O.Nachtmann@thphys.uni-heidelberg.de

Received: 31 August 2005
Revised: 15 December 2005
Published online: 9 March 2006

Abstract

We present a study of anomalous electroweak gauge-boson couplings that can be measured in e⁺e^- and γγ collisions at a future linear collider like ILC. We consider the gauge-boson sector of a locally SU(2)×U(1) invariant effective Lagrangian with ten dimension-six operators added to the Lagrangian of the standard model. These operators induce anomalous three-gauge-boson and four-gauge-boson couplings and an anomalous γγH coupling. We calculate the reachable sensitivity for the measurement of the anomalous couplings in γγ→WW. We compare these results with the reachable precision in the reaction e⁺e^-→WW on the one hand and with the bounds that one can obtain from high-precision observables in Z decays on the other hand. We show that one needs both the e⁺e^- and the γγ modes at an ILC to constrain the largest possible number of anomalous couplings and that the Giga-Z mode offers the best sensitivity for certain anomalous couplings.