Collider signals of $W'$ and $Z'$ bosons in the gauge-Higgs unification

TL;DR

This paper investigates collider signals of Kaluza-Klein excitations of gauge bosons in gauge-Higgs unification models, predicting their masses, decay channels, and potential observability at the LHC, with implications for new physics detection.

Contribution

It provides detailed calculations of decay rates, cross sections, and collider signatures of $W'$ and $Z'$ bosons in gauge-Higgs unification, including their masses and experimental prospects.

Findings

$W'$ and $Z'$ resonances appear around 6-8.5 TeV depending on model parameters.

Expected $ o$ about ten muon pair events at 3-7 TeV with 30 fb$^{-1}$ at 13 TeV LHC.

Unitarity is preserved in $WZ$ processes when all KK states are included.

Abstract

In the $SO(5)\times U(1)$ gauge-Higgs unification (GHU), Kaluza-Klein (KK) excited states of charged and neutral vector bosons, $W^{(1)}$, $W_R^{(1)}$, $Z^{(1)}$, $\gamma^{(1)}$ and $Z_R^{(1)}$, can be observed as $W'$ and $Z'$ signals in collider experiments. In this paper we evaluate the decay rates of the $W'$ and $Z'$, and $s$-channel cross sections mediated by $W'$ and $Z'$ bosons with final states involving the standard model (SM) fermion pair ($\ell \nu$, $\ell\bar{\ell}$, $q\bar{q}'$), $WH$, $ZH$, $WW$ and $WZ$. $W'$ and $Z'$ resonances appear around 6.0 TeV (8.5 TeV) for $\theta_H=0.115$ (0.0737) where $\theta_H$ is the Aharonov-Bohm phase in the fifth dimension in GHU. For decay rates we find $\Gamma(W'\to WH) \simeq \Gamma(W'\to WZ)$ ($W'=W^{(1)}$, $W_R^{(1)}$), $\Gamma(W^{(1)}\to WH,WZ) \sim\Gamma(W_R^{(1)}\to WH,WZ)$, $\Gamma(Z^{(1)}\to ZH) \simeq\sum_{Z'=Z^{(1)},\gamma^{(1)}}\Gamma(Z'\to WW)$, and $\Gamma(Z_R^{(1)}\to ZH) \simeq \Gamma(Z_R^{(1)}\to WW)$. $W'$ and $Z'$ signals of GHU can be best found at the LHC experiment in the processes $pp\to W' (Z')+X$ followed by $W'\to t\bar{b}$, $WH$, and $Z'\to e^+ e^-$, $\mu^+\mu^-, ZH$. For the lighter $Z'$ ($\theta_H = 0.115$) case, with forthcoming 30 fb$^{-1}$ data of the 13 TeV LHC experiment we expect about ten $\mu^+\mu^-$ events for the invariant mass range 3 to 7 TeV, though the number of the events becomes much smaller when $\theta_H=0.0737$. In the process with $WZ$ in the final state, it is confirmed that the unitarity is preserved, provided that all KK excited intermediate states are taken into account. Deviation of the $WWZ$ coupling from the SM is very tiny. Exotic partners $t_T^{(1)}$ and $b_Y^{(1)}$ of the top and bottom quarks with electric charge $+5/3$ and $-4/3$ have mass $M_{t_T^{(1)},b_Y^{(1)}}\simeq 4-5$ TeV, becoming the lightest non-SM particles in GHU which can be singly produced in collider experiments.