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

TL;DR

This study evaluates the potential to detect Higgs boson pair production via the $3 \ell 2 j$ + missing $E_T$ channel at the LHC and future 100 TeV colliders, focusing on signal discrimination and Higgs self-coupling measurement.

Contribution

It introduces a partial reconstruction method and analyzes key observables like $m_{T2}$ to improve sensitivity to Higgs pair production and the Higgs self-coupling at high-energy colliders.

Findings

Sensitivity at 14 TeV can reach 1.5 sigma for the SM.

At 100 TeV, sensitivity can reach 13 sigma for the SM.

Higgs self-coupling $\\lambda_3$ can be constrained within [-1,8] at 95\% CL at 14 TeV.

Abstract

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 \mu^\mp $ and $\mu^\pm \mu^\pm e^\mp$. 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 $\sigma$ for the Standard Model and the triple coupling of Higgs boson $\lambda_3$ 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 $\sigma$ for the Standard Model and we find that all values of $\lambda_3$ in the effective theory can be covered up to 3$\sigma$ even without optimising signals. To precisely measure the triple coupling of Higgs boson $\lambda_3=1$ 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 $\chi^2$ analysis, we find that it can be determined into a range [0.8, 1.5] at $95\%$ confidence level.