Collider signals of $W^{\prime }$ and $Z^{\prime }$ bosons in the gauge-Higgs unification

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 $W^{\prime }$ and $Z^{\prime }$ signals in collider experiments. In this paper we evaluate the decay rates of the $W^{\prime }$ and $Z^{\prime }$, and $s$-channel cross sections mediated by $W^{\prime }$ and $Z^{\prime }$ bosons with final states involving the standard model (SM) fermion pair ($\ell \nu$, $\ell \bar{\ell }$, $q{\bar{q}}^{\prime }$), $WH$, $ZH$, $WW$ and $WZ$. $W^{\prime }$ and $Z^{\prime }$ 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 $\Gamma (W^{\prime }\to WH)\simeq \Gamma (W^{\prime }\to WZ)$ ($W^{\prime }=W^{(1)}$, $W_R^{(1)}$), $\Gamma (W^{(1)}\to WH,WZ)\sim \Gamma (W_R^{(1)}\to WH,WZ)$, $\Gamma (Z^{(1)}\to ZH)\simeq {\sum }_{Z^{\prime }=Z^{(1)},{\gamma }^{(1)}}\Gamma (Z^{\prime }\to WW)$, and $\Gamma (Z_R^{(1)}\to ZH)\simeq \Gamma (Z_R^{(1)}\to WW)$. $W^{\prime }$ and $Z^{\prime }$ signals of GHU can be best found at the LHC experiment in the processes $pp\to W^{\prime }(Z^{\prime })+X$ followed by $W^{\prime }\to t\bar{b}$, $WH$, and $Z^{\prime }\to e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-},ZH$. For the lighter $Z^{\prime }$ (${\theta }_H=0.115$) 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.

Comments: 66 pages, 10 figures, 18 tables (v2) typos corrected, reference added (v3) comments added (v4) match the published version