Probing the mechanism of EWSB with a rho parameter defined in terms of Higgs couplings

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A definition of the rho parameter based on the Higgs couplings with the gauge bosons, rhoₕ= ghWW/c²W ghZZ, is proposed as a new probe into the origin of the mechanism of electroweak symmetry breaking. While ρₕ=1 holds in the SM, deviations from one are predicted in models with extended Higgs sector. We derive a general expresion of rhoₕ for a model with arbitrary Higgs multiplets, and discuss its size within the context of specific models with Higgs triplets, including the ``Little Higgs'' models recently proposed. We find the even for Higgs models that incorporate the custodial symmetry to make rho=1, one could have rhoₕ≠ 1, which could be tested at the level of a few percent, with the precision Higgs meassurements expected at the NLC.