Paper detail

Probe Higgs boson pair production via the $3 \ell 2 j$ + missing $E_T$ mode

We perform a detailed hadron-level study on the sensitivity of Higgs boson pair production via the $WW^{*}WW^{*}$ channel with the final state $3 \ell 2 j$ + missing $E_T$ at the LHC with the collision energy $\sqrt{S} = 14$ TeV and a future 100 TeV collider. To avoid the huge background from $pp \to Z W + \textrm{jets}$ processes, we confine to consider the four lepton patterns: $e^\pm e^\pm μ^\mp $ and $μ^\pm μ^\pm e^\mp$. We propose a partial reconstruction method to determine the most reliable combination. After that, we examine a few crucial observables which can discriminate efficiently signal and background events, especially we notice that the observable $m_{\rm T2}$ is very efficient. For the LHC 14 TeV collisions, with an accumulated 3000 fb$^{-1}$ dataset, we find that the sensitivity of this mode can reach up to 1.5 $σ$ for the Standard Model and the triple coupling of Higgs boson $λ_3$ in the simplest effective theory can be constrained into the range [-1, 8] at $95\%$ confidence level; at a 100 TeV collider with the integrated luminosity 3000 fb$^{-1}$, the sensitivity can reach up to 13 $σ$ for the Standard Model and we find that all values of $λ_3$ in the effective theory can be covered up to 3$σ$ even without optimising signals. To precisely measure the triple coupling of Higgs boson $λ_3=1$ of the Standard Model at a 100 TeV collider, by using the invariant mass of three leptons which is robust to against the contamination of underlying events and pileup effects and by performing a $χ^2$ analysis, we find that it can be determined into a range [0.8, 1.5] at $95\%$ confidence level.