[Paper Review] Ultraviolet Complete Technicolor and Higgs Physics at LHC

Matti Antola, Stefano Di Chiara+1 more|arXiv (Cornell University)|Jul 17, 2013

Computational Physics and Python Applications4 citations

TL;DR

This paper proposes an ultraviolet-complete Technicolor model, SU(3) Minimal Walking Technicolor (3MWT), where elementary scalars and gauginos are decoupled above the electroweak scale, avoiding the little hierarchy problem. The model realizes electroweak symmetry breaking via global SU(3) symmetry breaking to SO(3), reproducing LHC Higgs data with precision comparable to the Standard Model, while providing a dynamical explanation for fermion masses and flavor structure without elementary scalars.

ABSTRACT

We construct a Technicolor model which provides masses for the electroweak gauge bosons and for all the Standard Model matter fields. Starting from an ultraviolet complete supersymmetric technicolor, we propose a scenario where all elementary scalars, gauginos, and higgsinos are decoupled at an energy scale substantially higher than the electroweak scale, therefore avoiding the little hierarchy problem of the minimal supersymmetric standard model. The resulting low energy theory has an SU(3) global symmetry whose breaking to SO(3) leads to electroweak symmetry breaking. We study in detail the phenomenology of this theory and demonstrate that it reproduces the present LHC data at the same level of precision as the Standard Model itself.

Motivation & Objective

• To construct a UV-complete Technicolor model that avoids the little hierarchy problem by decoupling elementary scalars and gauginos above the electroweak scale.
• To demonstrate that electroweak symmetry breaking arises from global SU(3) symmetry breaking to SO(3), leading to a composite Higgs-like state.
• To show that the model reproduces LHC Higgs data with precision comparable to the Standard Model, including Higgs couplings and precision electroweak observables.
• To provide a dynamical explanation for fermion masses and flavor hierarchies without elementary Higgs fields or fine-tuning.

Proposed method

• Starting from a supersymmetric Technicolor framework, the model integrates out all elementary scalars, gauginos, and higgsinos at a scale well above the TeV scale.
• The low-energy effective theory features three Weyl technifermions, a technigluon, and a heavy fourth-generation EW doublet of leptons, with an SU(3) global symmetry.
• Electroweak symmetry breaking is driven by the spontaneous breaking of SU(3) global symmetry to SO(3), generating a pseudo-Nambu-Goldstone boson responsible for the Higgs-like state.
• The model computes S and T parameters using a general neutrino mass matrix, with contributions from heavy vector-like leptons and neutralinos, ensuring compatibility with precision electroweak data.
• Fermion masses arise from attractive Yukawa couplings between SM fermions and composite technibaryons, replacing the need for elementary Higgs fields.
• The mesonic Lagrangian is derived from the underlying UV theory, with mass matrices for neutral and charged gauge bosons computed explicitly to match LHC constraints.

Experimental results

Research questions

• RQ1 Can a UV-complete Technicolor model avoid the little hierarchy problem by decoupling elementary scalars and gauginos while preserving electroweak symmetry breaking?
• RQ2 Does a model with SU(3) global symmetry breaking to SO(3) reproduce the observed Higgs boson mass and couplings at the LHC?
• RQ3 How do fermion masses and flavor hierarchies emerge in a composite Higgs framework without elementary Higgs fields?
• RQ4 What are the contributions of heavy vector-like leptons and neutralinos to the S and T parameters in a composite Higgs model?
• RQ5 Can the model achieve precision electroweak agreement with the Standard Model while remaining natural and free of fine-tuning?

Key findings

• The model successfully reproduces the observed Higgs boson mass of 125 GeV through loop corrections from heavy SM states, without requiring an elementary Higgs.
• The S and T parameters are computed using a general neutrino mass matrix, and the results are consistent with current LHC precision electroweak data.
• The model achieves compatibility with LHC Higgs data at the same level of precision as the Standard Model, despite the absence of elementary scalars.
• Fermion masses arise from attractive Yukawa interactions between SM fermions and composite states, providing a dynamical explanation for flavor hierarchies.
• The low-energy spectrum consists of SM fields, three Weyl technifermions, a technigluon, and a heavy fourth-generation EW doublet, with no light elementary scalars.
• The model avoids the little hierarchy problem by decoupling all elementary scalars and gauginos at a scale well above the TeV scale, preserving naturalness.