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Higgs decays in the Two Higgs Doublet Model: Large quantum effects in the decoupling regime

We study the Higgs-boson decays h0 -> b \bar{b}, h0 -> γγand h0 -> γZ within the framework of the Two Higgs Doublet Model (THDM) in the context of the decoupling regime, together with tree level unitarity constraints. We show that when the light CP-even Higgs boson of the THDM mimics the Standard-Model Higgs boson, not only the one-loop effects to h0 -> {γγ,γZ} but also the one-loop contribution to h0 -> b \bar{b} can be used to distinguish between THDM and SM. The size of the quantum effects in h0 -> b \bar{b} are of the same order as in h0 -> {γγ,γZ} and can reach 25% in both cases.