Collider Phenomenology of Gauge-Higgs Unification Scenarios in Warped Extra Dimensions

TL;DR

This study develops and applies a consistent 5D Gauge-Higgs Unification framework in warped extra dimensions (RS1 with bulk SO(5)×U(1)_X) to compute zero-mode and KK-mode couplings for gluons, W, Z, and the Higgs to third-generation quarks. By solving for gauge and fermion wavefunctions in the presence of a Higgs vev, it derives overlap-based couplings, decay widths, and the resulting collider phenomenology, with a focus on the first KK top t^1 and the first KK gluon G^1. It shows that in the linear regime, SM-like couplings are recovered up to KK corrections, while numerically, t^1 states are light and strongly coupled to G^1, which decays predominantly to t^1 t^1, boosting t^1 production beyond direct QCD production. At the LHC, two benchmark points demonstrate that G^1-induced t^1 production can yield a 3–5σ discovery reach for m_{t^1} up to about 1.5 TeV with 300 fb^{-1}, using boosted-W and massive-jet techniques to reconstruct t^1; this provides a practical pathway to probe Gauge-Higgs Unification scenarios compatible with EW precision tests.

Abstract

We compute the couplings of the zero modes and first excited states of gluons, $W$'s, $Z$ gauge bosons, as well as the Higgs, to the zero modes and first excited states of the third generation quarks, in an RS Gauge-Higgs unification scenario based on a bulk $SO(5)\times U(1)_X$ gauge symmetry, with gauge and fermion fields propagating in the bulk. Using the parameter space consistent with electroweak precision tests and radiative electroweak symmetry breaking, we study numerically the dependence of these couplings on the parameters of our model. Furthermore, after emphasizing the presence of light excited states of the top quark, which couple strongly to the Kaluza Klein gauge bosons, the associated collider phenomenology is analyzed. In particular, we concentrate on the possible detection of the first excited state of the top, $t^1$, which tends to have a higher mass than the ones accessible via regular QCD production processes. We stress that the detection of these particles is still possible due to an increase in the pair production of $t^1$ induced by the first excited state of the gluon, $G^1$.

Figures (19)

• Figure 1: $g_{G^1\bar{t}t}/g_s(\tilde{k})$ vs $c_{1}$. As $c_1$ grows, the coupling for both chiralities unify.
• Figure 2: $g_{G^1\bar{t^1}t^1}/g_s(\tilde{k})$ vs $c_{1}$. As $c_1$ grows, the left-handed coupling remains constant and the right-handed one grows.
• Figure 3: $g_{Z\bar{t^1}t}/g_w(\tilde{k})$ vs $m_{t^1}$ (TeV), where $g_w(\tilde{k})=g_5/\sqrt{L}$. Notice the $1/m_{t^1}$ dependence of $g_{Z\bar{t^1}_Lt_L}$.
• Figure 4: Branching ratios for the decay of $t^1$ vs $m_{t^1}$ (GeV). Notice that the 2:1:1 relations holds for large $m_{t^1}$.
• Figure 5: Branching ratios for the decay of $G^1$ vs $m_{G^1}$ (GeV). Notice that $G^1$ decays mostly to $t^1$ pairs.