Abstract
We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu-Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu-Goldstone bosons, and show they can decay fast enough without cosmological problems. We further evaluate the energy dependences of the couplings between elementary fields perturbatively, and find that our model is the first one which realizes the flatland scenario with the dimensional transmutation by the strong coupling dynamics. Similarly to the conventional flatland model with Coleman-Weinberg mechanism, the electroweak vacuum in our model is meta-stable.
Highlights
The origin of the electroweak symmetry breaking (EWSB) remains a mystery
In the standard model (SM), the EWSB requires a negative mass squared for the Higgs doublet scalar field, whose magnitude is set by hand
As an interesting possibility, let us consider whether the scalar potential vanishes at the Planck scale. This constraint is severer than the scale invariant condition, and all the scalar quartic couplings must be zero at the Planck scale. This situation has been studied in so-called flatland scenario [8, 10, 13, 15], where a singlet scalar field has an interaction with the SM Higgs doublet, and its vacuum expectation values (VEVs) induces negative mass squared of the Higgs [6, 8, 10, 13, 15, 20]
Summary
The origin of the electroweak symmetry breaking (EWSB) remains a mystery. In the standard model (SM), the EWSB requires a negative mass squared for the Higgs doublet scalar field, whose magnitude is set by hand. In the model with an additional U(1) gauge symmetry, the scale invariance is broken by the Coleman-Weinberg mechanism [28], and if the breaking scale is not so far from the electroweak (EW) scale, there is no gauge hierarchy problem. The origin of the EWSB is not necessary and inevitable in this scenario, and we are going to try the dynamical realization of negative mass squared by the bosonic seesaw mechanism [31]. Though the chiral symmetry breaking happens by techni-fermion condensations, the EWSB does not happen by this strong coupling TC dynamics itself. To avoid massless Nambu-Goldstone (NG) bosons by the chiral symmetry breaking in strong coupling sector, we introduce a real pseudo-scalar singlet field and its interactions with techni-fermions and Higgs doublet. To the conventional flatland model with Coleman-Weinberg mechanism, the EW vacuum in our model is meta-stable
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