Higgs-boson couplings beyond the Standard Model

The implications for Higgs decays of potential new physics beyond the Standard Model (BSM) are considered in the context of effective field theory, assuming perturbative decoupling. Using existing data to restrict which dimension-six operators can arise, it is shown that, given the existing experimental constraints, only a small number of operators can affect the decays of the Higgs: those that may be potentially-tree-generated (PTG) and modify the Higgs-fermion couplings, or those that may be loop-generated (LG) that modify the Higgs couplings to γγ, Zγ and GG. Implications for specific branching ratios are given in terms of the coefficients of various dimension-six operators. In such a scenario, the ratios Γ(H→WW⁎)/Γ(H→ZZ⁎) and Γ(H→Wℓν)/Γ(H→Zℓℓ) equal to their Standard Model values to an accuracy of O(1%) or less.