Novel universality and Higgs decay H → γ γ, gg in the SO(5) x U(1) gauge-Higgs unification

The SO(5) x U(1) gauge-Higgs unification in the Randall-Sundrum warped space with the Higgs boson mass m(H) = 126 GeV is constructed. A universal relation is found between the Kaluza-Klein (KK) mass scale m(KK) and the Aharonov-Bohm (AB) phase theta(H) in the fifth dimension; m(KK) similar to 1350 GeV/(sin theta(H))(0.787). The cubic and quartic self-couplings of the Higgs boson become smaller than those in the standard model (SM), having universal dependence on theta(H). The decay rates H -> gamma gamma, gg are evaluated by summing contributions from KK towers. Corrections coming from KK excited states are finite and about 0.2% (2%) for theta(H) = 0.12 (0.36), branching fractions of various decay modes of the Higgs boson remaining nearly the same as in the SM. The signal strengths of the Higgs decay modes relative to the SM are similar to cos(2) theta(H). The mass of the first KK Z is predicted to be 5.9 (2.4) TeV for theta(H) = 0.12 (0.36). We also point out the possible enhancement of Gamma (H -> gamma gamma) due to the large U(1)(x) charge of new fermion multiplets. (C) 2013 Elsevier B.V. All rights reserved.