Measuring Trilinear Higgs Coupling in $WHH$ and $ZHH$ Productions at the HL-LHC

Abstract

Determination of trilinear Higgs coupling ($\hat{I}{»}_{HHH}=\hat{I}º\hat{I}{»}_{HHH}^{\mathrm{SM}}$) through Higgs pair productions is a major motivation for the LHC high luminosity phase. We perform a detailed collider simulation to explore the potential of measuring $\hat{I}{»}_{HHH}$ in the $VHH$ ($V=W,Z$) production at the HL-LHC. We find that the trilinear Higgs coupling in the SM ($\hat{I}{»}_{HHH}^{\mathrm{SM}}$) could be measured at the level of $1.3\ddot{I}ƒ$. Combining with the gluon fusion, vector boson fusion and $t\bar{t}HH$ channels, $\hat{I}{»}_{HHH}^{\mathrm{SM}}$ is expected to be measured at the level of $3.13\ddot{I}ƒ$. If no evidence of Higgs pair productions were observed, the $VHH$ production, together with the gluon fusion channel, would impose a bound of $0.5\le \hat{I}º\le 2.2$ at the 95\% confidence level.