Radiative Corrections to Scalar Masses and Mixing in a Scale Invariant Two Higgs Doublet Model

We study the Higgs-boson mass spectrum of a classical scale-invariant realization of the two-Higgs-doublet model (SI-2HDM). The classical scale symmetry of the theory is explicitly broken by quantum loop effects due to gauge interactions, Higgs self-couplings and top-quark Yukawa couplings. We determine the allowed parameter space compatible with perturbative unitarity and electroweak precision data. Taking into account the LEP and the recent LHC exclusion limits on a Standard-Model-like Higgs boson H_SM, we obtain rather strict constraints on the mass spectrum of the heavy Higgs sector of the SI-2HDM. In particular, if M_{H_SM} \sim 125 GeV, the SI-2HDM strongly favours scenarios, in which at least one of the non-standard neutral Higgs bosons has a mass close to 400 GeV and is generically degenerate with the charged Higgs boson, whilst the third neutral Higgs scalar is lighter than ~ 500 GeV.