New Physics Contribution to Neutral Trilinear Gauge Boson Couplings

We study the one-loop new physics effects to the CP even triple neutral gauge boson vertices γ ⋆ γ Z, γ ⋆ Z Z, Z ⋆ Z γ and Z ⋆ ZZ in the context of Little Higgs models. We compute the contribution of the additional fermions in Little Higgs models in the framework of direct product groups where [SU(2)×U(1)]2 gauge symmetry is embedded in SU(5) global symmetry and also in the framework of the simple group where SU(N)×U(1) gauge symmetry breaks down to SU(2) L ×U(1). We calculate the contribution of the fermions to these couplings when T parity is invoked. In addition, we re-examine the MSSM contribution at the chosen point of SPS1a′ and compare with the SM and Little Higgs models.