DEVIATIONS FROM LOW-ENERGY THEOREM FOR VLVL SCATTERING DUE TO PSEUDO-GOLDSTONE BOSONS

Abstract

Possible deviations from a low-energy theorem for the scattering of strongly interacting longitudinally polarized W and Z bosons are discussed within a particular scheme of electroweak symmetry breaking. The scheme (suggested earlier by other authors in a slightly different context) is based on spontaneous breakdown of an SU(4) symmetry to custodial SU(2) subgroup. The physical spectrum of such a model contains a set of relatively light pseudo-Goldstone bosons whose interactions with vector bosons modify the low-energy theorem proven for a "minimal" symmetry-breaking sector The Goldstone-boson manifold SU(4)/SU(2) is not a symmetric space. In this context it is observed that, on the other hand, there is a large class of models of electroweak symmetry breaking, involving groups G and H such that the G/H is a symmetric space and the corresponding rich multiplets of pseudo-Goldstone bosons do not influence the canonical low-energy theorem. For the scheme considered here, the relevant interactions are described in terms of an effective chiral Lagrangian and tree-level contributions of the pseudo-Goldstone boson exchanges to the vector boson scattering are computed explicitly. A comparison with the standard model is made.