Probing the minimal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>U</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1</mml:mn><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mi>X</mml:mi></mml:msub></mml:math> model at future electron-positron colliders via fermion pair-production channels
Arindam Das, P. S. Bhupal Dev, Yutaka Hosotani, Sanjoy Mandal
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 (${Z}^{\ensuremath{'}}$) 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 ${e}^{\ensuremath{-}}{e}^{+}$ colliders: ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}f\overline{f}$. Apart from the standard $\ensuremath{\gamma}$ and $Z$-mediated processes, this model features additional $s$-channel (or both $s$ and $t$-channel when $f={e}^{\ensuremath{-}}$) ${Z}^{\ensuremath{'}}$ exchange which interferes with the SM processes. We first estimate the bounds on the $U(1{)}_{X}$ coupling $({g}^{\ensuremath{'}})$ and the ${Z}^{\ensuremath{'}}$ mass $({M}_{{Z}^{\ensuremath{'}}})$ considering the latest dilepton and dijet constraints from the heavy resonance searches at the LHC. Then using the allowed values of ${g}^{\ensuremath{'}}$, 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 $f\overline{f}$ 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 ${Z}^{\ensuremath{'}}$ bosons at future ${e}^{+}{e}^{\ensuremath{-}}$ colliders.