Anomalous Higgs Boson Production and Decay

A non-standard symmetry breaking sector may lead to derivative couplings of the Higgs boson and thereby to anomalous interactions with the electroweak gauge bosons. In the framework of gauge-invariant effective Lagrangians the resulting changes in Higgs boson production and decay mechanisms are related to anomalous triple vector boson couplings. Using low energy constraints on the dimension-six operators in the effective Lagrangian, we discuss the size of deviations from SM predictions which may be expected in Higgs boson production and decay rates. Large enhancements are allowed e.g. in the Z → Hγ and H → γγ partial decay widths, leading to Z → γγγ events at LEP. In recent years the standard model (SM) of electroweak interactions has been beautifully confirmed, in particular via the LEP experiments. Z production via ee annihilation and the bulk of the Z decay processes mainly probe the couplings of the quarks and leptons to the Z boson, however. While the gauge theory predictions of these fermion-Zcouplings have now been comfirmed at the 1% level or better, the bosonic sector of the SM has been tested to a much lesser degree because present accelerators largely operate below weak boson pair production or Higgs production threshold. In order to find out how the SU(2)⊗ U(1) symmetry of the SM is broken in nature, an experimental determination is needed of the interactions between the gauge bosons and the remnants of the order parameter which gives rise to the spontaneous breaking of the gauge symmetry, i.e. the Higgs boson in the SM. In this letter we investigate the phenomenology of models which are relatively close to the SM in that they posess a (possibly light) Higgs scalar as the remnant of the SU(2) doublet order parameter. The anomalous interactions of this doublet field Φ, which posesses the same quantum numbers as the SM Higgs doublet field, can conveniently be described by an effective Lagrangian Leff = ∑