Probing nonstandard bosonic interactions via W-boson pair production at   lepton colliders
  The process e+e- --> W+W- provides a valuable laboratory to test the Standard Model (SM) and to search for new physics. The most general helicity amplitudes for this process require the introduction of nine form-factors which we calculate in the context of SU(2) X U(1) gauge-invariant extensions of the SM. The contributions of new physics are parametrized via an effective Lagrangian constructed from the light fields. Because the mechanism of electroweak symmetry-breaking remains an open problem we consider both the effective Lagrangian with a linearly realized Higgs sector, i.e. with a light physical Higgs boson, and the effective Lagrangian which utilizes a nonlinear realization of the Higgs mechanism. The use of an effective Lagrangian allows one to calculate consistently nonstandard contributions to e+e- --> W+W- amplitudes as well as the nonstandard contributions to other processes. We study the interplay of the low-energy and Z-pole measurements with measurements via the processes e+e- --> fermion pairs and e+e- --> W+W- at LEP II or a future linear e+e- collider. Concrete relationships between operators of the linear and nonlinear realizations are presented where possible. 
K. Hagiwara, T. Hatsukano, S. Ishihara and R. Szalapski