Electroweak-Higgs Unification in the Two Higgs Doublet Model: Masses and Couplings of the Neutral and Charged Higgs Bosons

Abstract

We obtain the mass spectrum and the Higgs self-coupling of the two Higgs doublet model (THDM) in an alternative unification scenario where the parameters of the Higgs potential $λ_i$ ($i=1,2,3,4,5$) are determined by imposing their unification with the electroweak gauge couplings. An attractive feature of this scenario is the possibility to determine the Higgs boson masses by evolving the $λ_i$,s from the electroweak-Higgs unification scale $M_{GH}$ down to the electroweak scale. The unification condition for the gauge ($g_1,g_2$) and Higgs couplings is written as $g_1=g_2=f(λ_i)$, where $g_1=k_Y^{1/2} g_Y$, and $k_Y$ being the normalization constant. Two variants for the unification condition are discussed; Scenario I is defined through the linear relation: $g_1=g_2=k_H(i)λ_i(M_{GH})$, while Scenario II assumes a quadratic relation: $g^2_1=g^2_2=k_H(i)λ_i(M_{GH})$. Working in Scenario I, fixing {\it ad hoc} $-k_H(5)={1/2} k_H(4)={3/2} k_H(3)=k_H(2)=k_H(1) =1$, taking $\tanβ=1$ and using the standard normalization ($k_Y=5/3$), we obtain the following spectrum for the Higgs boson masses $m_{h^0} = 109.1$ GeV, $m_{H^0} = 123.2$ GeV, $m_{A^0} = 115.5$ GeV, and $m_{H^{\pm}} = 80.3$ GeV, with similar results for other normalizations such as $k_Y=3/2$ and $k_Y=7/4$.