Exploring correlations between HEFT Higgs couplings κV and κ2V via HH production at e+e- colliders

Abstract

In this work we explore the phenomenological implications at future $e^{+}{e}^{-}$ colliders of assuming anomalous couplings of the Higgs boson to gauge bosons HVV and HHVV$(V=W,Z)$ given by the $\kappa$-modifiers with respect to the Standard Model couplings, ${\kappa }_V$ and ${\kappa }_{2V},$ respectively. For this study we use the Higgs Effective Field Theory (HEFT) where these two $\kappa$ parameters are identified with the two most relevant effective couplings at leading order, concretely $a={\kappa }_V$ and $b={\kappa }_{2V}.$ Our focus is put on these two couplings and their potential correlations which we believe carry interesting information on the underlying ultraviolet theory. The particular studied process is $e^{+}{e}^{-}\to HH\nu \overline{\nu },$ where the vector boson scattering subprocess $WW\to HH$ plays a central role, specially at the largest planned energy colliders. Our detailed study of this process as a function of the energy and the angular variables indicates that the produced Higgs bosons in the BSM scenarios will have in general a high transversality as compared to the SM case if ${\kappa }_V^2\ne {\kappa }_{2V}.$ In order to enhance the sensitivity to these HEFT parameters ${\kappa }_V$ and ${\kappa }_{2V}$ and their potential correlations we propose here some selected differential cross sections for the $e^{+}{e}^{-}\to HH\nu \overline{\nu }$ process, where different kinematic properties of the BSM case with respect to the SM are manifested. Finally, we will focus on the dominant Higgs decays to $b\overline{b}$ pairs leading to final events with 4 b-jets and missing transverse energy from the undetected neutrinos and will provide the expected accessibility to the $({\kappa }_V,{\kappa }_{2V})$ effective couplings and their potential correlations. In our study we will consider the three projected energies for $e^{+}{e}^{-}$ colliders of 500 GeV, 1000 GeV and 3000 GeV.