Dark-technicolour at colliders

TL;DR

The paper develops a Dark-technicolor (DTC) framework based on $G=SU(N_{TC})\times SU(N_{DTC})\times SU(N_D)$ that generates electroweak symmetry breaking dynamically and addresses SM flavor via the Standard Hierarchical VEVs Model (SHVM). It leverages the Extended Most Attractive Channel (EMAC) hypothesis to produce a hierarchy of multi-fermion condensates, enabling realistic fermion masses and mixings while keeping the Higgs as a composite state. Experimental constraints, particularly the S parameter, favor a heavy vector spectrum with $M_{\rho_{TC}}$ near $2~\mathrm{TeV}$, compatible with lattice-inspired scaling at $N_{TC}=3$. The low-energy realization favors SHVM over Froggatt–Nielsen within DTC, with detailed collider phenomenology predicting observable DTC-sector signals at HL-LHC, HE-LHC, and future 100 TeV colliders in channels like $\bar{b}b$, $\tau^+\tau^-$, $t\bar{t}$, and $\gamma\gamma$, while TC bound-state couplings to SM fermions remain highly suppressed. The work provides a coherent, strongly-coupled path to both mass generation and flavor, with concrete predictions for the scalar and pseudoscalar spectra and collider reach.

Abstract

We demonstrate that QCD-like gauge dynamics can be consistently embedded within the Dark Technicolor paradigm by invoking the extended Most Attractive Channel hypothesis, thereby revitalizing conventional technicolor scenarios. In this framework, the Higgs mass is generated dynamically while remaining consistent with electroweak precision tests, including constraints from the $S$ parameter. The flavor problem is resolved by incorporating the Standard Hierarchical VEVs Model, whereas a simple Froggatt--Nielsen construction is shown to be incompatible. Couplings of techni-hadrons such as $ρ_{\rm TC}$ and $η_{\rm TC}^\prime$ to Standard Model fermions are highly suppressed, leading to negligible direct fermionic signatures. Nevertheless, DTC mesons remain testable at the HL-LHC, HE-LHC, and future 100~TeV collider, with promising discovery channels including $\bar{b}b$, $τ^+τ^-$, $t\bar{t}$, and $γγ$.

Figures (13)

• Figure 1: Possible behaviors of $M/f_\pi$, with $f_\pi=F_{\Pi_{\rm TC}}$, in an $\rm SU(N_{\rm TC})$ gauge theory at fixed fermion flavor number $N_f$. The solid line shows $M/f_\pi \propto 1/\sqrt{\rm N_{\rm TC}}$ at large $\rm N_{\rm TC}$, saturating the bound in Eq. \ref{['eq:NDA-bound']} at intermediate $\rm N_{\rm TC}$, and eventually losing asymptotic freedom at very small $\rm N_{\rm TC}$. The dashed line represents a monotonic decrease without saturation. Adapted from Ref. Chivukula:1992nw.
• Figure 2: The mass generation of the techni-rho meson from the DQCD dynamics. The blob denotes either the formation of a meson or a condensate.
• Figure 3: At low energies, the DTC paradigm may effectively reduce to either the SHVM or the FN mechanism.
• Figure 4: The Feynman diagrams for the masses of charged fermions in the DTC paradigm. The top part shows the generic interactions of the SM, TC, DQCD and DTC fermions. In the lower part of figure, the formations of the TC chiral condensates, $\langle \varphi \rangle$ (circular blob), a generic multi-fermion chiral condensates $\langle \chi_r \rangle$ (collection of circular blobs), and the resulting mass of the SM charged fermion is depicted.
• Figure 5: The Feynman diagrams for the masses of neutrinos in the DTC paradigm. On the top, there are generic interactions involving the SM, TC, DQCD and DTC gauge sectors mediated by ETC, EDTC and GUT gauge bosons. In the bottom, we show the generic Feynman diagram after the formation of the fermionic condensates.