Probing the minimal $U(1{)}_X$ model at future electron-positron colliders via the fermion pair-production channel

Abstract

The minimal $U(1{)}_X$ extension of the Standard Model (SM) is a well-motivated new physics scenario, where anomaly cancellation dictates new neutral gauge boson ($Z^{\prime }$) couplings with the SM fermions in terms of the $U(1{)}_X$ charges of the new scalar fields. We investigate the SM charged fermion pair-production process for different values of these $U(1{)}_X$ charges at future $e^{-}{e}^{+}$ colliders: $e^{+}{e}^{-}\to f\bar{f}$. Apart from the standard $\gamma$ and $Z$-mediated processes, this model features additional $s$-channel (or both $s$ and $t$-channel when $f=e^{-}$) $Z^{\prime }$ exchange which interferes with the SM processes. We first estimate the bounds on the $U(1{)}_X$ coupling $(g^{\prime })$ and the $Z^{\prime }$ mass $(M_{Z^{\prime }})$ considering the latest dilepton and dijet constraints from the heavy resonance searches at the LHC. Then using the allowed values of $g^{\prime }$, we study the angular distributions, forward-backward $({\mathcal{A}}_{\mathrm{FB}})$, left-right $({\mathcal{A}}_{\mathrm{LR}})$ and left-right forward-backward $({\mathcal{A}}_{\mathrm{LR},\mathrm{FB}})$ asymmetries of the $f\bar{f}$ final states. We find that these observables can show substantial deviations from the SM results in the $U(1{)}_X$ model, thus providing a powerful probe of the multi-TeV $Z^{\prime }$ bosons at future $e^{+}{e}^{-}$ colliders.

Comments: 51 pages. Typos in Higgs charges in Tab-II corrected. Results unaltered. Matched published version