Optimal estimation of Higgs-Gauge Boson couplings at the future $e^{+}{e}^{-}$ colliders

Abstract

The proposed $e^{+}{e}^{-}$ collider offers an ideal environment for precise estimation of Higgs boson properties which are of utmost importance to validate the Standard Model of particle physics. We investigate $hVV$ couplings, where $V\in \{Z,\gamma \}$ with single Higgs production associated with $Z$ boson at the proposed $e^{+}{e}^{-}$ machine with $\sqrt{s}=250$ GeV, within the Standard Model Effective Field Theory (SMEFT) framework. We employ the recoil mass of the dilepton system, to select the signal phase space, i.e, $Zh\to l^{+}{l}^{-}b\text{Bar}b$ events. The constraints on the Wilson coefficients (WCs) are obtained using the optimal observable technique (OOT). On comparison with the current experimental limits at $68\%$ CL with $138$ fb${}^{-1}$ luminosity, our limits are tighter by a factor ranging from $1.5-10$ for CP even operators, while CP-odd WCs shows comparable limits.

Comments: 12 pages, 6 figures, 3 tables. Accepted for publication in Physical Review D