Technicolor Walks at the LHC

TL;DR

This work analyzes walking technicolor as a dynamical mechanism for electroweak symmetry breaking using the Next-to-Minimal Walking Technicolor (NMWT) framework with SU(2)$_L\times$SU(2)$_R$ symmetry. It builds a chiral resonance Lagrangian including spin-0 and spin-1 states, constrains the spectrum via Weinberg sum rules and EW precision data, and investigates LHC phenomenology focusing on Drell–Yan and Vector Boson Fusion production of heavy vector resonances $R_{1,2}$ and the composite Higgs. The main findings show that heavy vector resonances can be produced and observed at the LHC via DY up to about $M\sim 2$ TeV (with $\tilde{g}=2$ offering the best reach in leptonic channels), while VBF is generally subleading; the associated production of the composite Higgs with gauge bosons can be significantly enhanced by these resonances. The results provide clear, testable footprints and parameter-space guidance for WT-like strongly coupled DEWSB theories at the LHC, and illustrate how higher-dimension operators (e.g., with coefficient $\gamma$) can modify widths without eliminating leptonic signals.

Abstract

We analyze the potential of the Large Hadron Collider (LHC) to observe signatures of phenomenologically viable Walking Technicolor models. We study and compare the Drell-Yan (DY) and Vector Boson Fusion (VBF) mechanisms for the production of composite heavy vectors. We find that the heavy vectors are most easily produced and detected via the DY processes. The composite Higgs phenomenology is also studied. If Technicolor walks at the LHC its footprints will be visible and our analysis will help uncovering them.

Figures (21)

• Figure 1: Contour plot for $a$ in the $(M_A,\tilde{g})$ plane, for $S=0.3$ in NMWT ($d({\rm R})=6$). We plot contours for $a=0,1,2,3$, and $3\leq a\leq a_{\rm max}=d({\rm R})/(2\pi S)\simeq 3.18$ (central region). The running regime corresponds to the $a=0$ contour, which is on the lower right of the parameter space. Walking dynamics requires $a={\cal O}(1)>0$, which is achieved for a large portion of the parameter space.
• Figure 2: Bounds, for $S=0.3$, in the $(M_A,\tilde{g})$ plane from: (i) CDF direct searches of $R_1^0$ at Tevatron, in $p\bar{p}\rightarrow e^+e^-$, for $s=1$ and $M_{H}=200$ GeV. The forbidden regions is the uniformly shaded one in the left corner. The parameters $M_H$ and $s$ affect indirectly the Tevatron bounds by changing the BR of the $Z$ boson decay to two composite Higgsses. However, we have checked that the effects on the constraints coming from varying the parameter $s$ and $M_H$ are small. (ii) Measurement of the electroweak parameters W and Y at 95% confidence level. The forbidden region is the striped one in the left corner. (iii) The constraint $a>0$, where $a$ is defined in Eq. (\ref{['eq:WSR2']}). The corresponding limiting curve is given by Eq. (\ref{['eq:MAbound']}). The forbidden region is the shaded one in the right corner. (iv) Consistency of the theory: no imaginary numbers for physical quantities like $F_V$ and $F_A$ . The forbidden region is the horizontal stripe in the upper part of the figure. The limiting curve here is given by Eq. (\ref{['eq:gtbounds']}). We repeat that the shaded regions are excluded.
• Figure 3: Mass splittings $M_V-M_A$ (left) and $M_{R_2^\pm}-M_{R_1^\pm}$ (right). The dotted lines are for $\tilde{g}=5$ while the solid lines are for $\tilde{g}=2$.
• Figure 4: The mass spectrum of the $M_{R^{\pm,0}_{1,2}}$ vector mesons versus $M_A$ for $\tilde{g}=2$ (left) and $\tilde{g}=5$ (right). The masses of the charged vector mesons are denoted by solid lines, while the masses of the neutral mesons are denoted by dashed lines.
• Figure 5: Decay width of the charged (first row) and neutral (second row) vector mesons for $S=0.3$ and $\tilde{g}=2,5$. We take $M_H = 0.2 \ \textrm{TeV},\ s=0$.