Double Higgs boson production and Higgs self-coupling extraction at CLIC

The Compact Linear Collider (CLIC) is a future electron–positron collider that will allow measurements of the trilinear Higgs self-coupling in double Higgs boson events produced at its high-energy stages with collision energies from √(s) = 1.4 to 3 TeV. The sensitivity to the Higgs self-coupling is driven by the measurements of the cross section and the invariant mass distribution of the Higgs-boson pair in the W-boson fusion process, e^+e^-→HHνν̅ . It is enhanced by including the cross-section measurement of ZHH production at 1.4 TeV. The expected sensitivity of CLIC for Higgs pair production through W-boson fusion is studied for the decay channels bb̅bb̅ and bb̅WW^* using full detector simulation including all relevant backgrounds at √(s) = 1.4 TeV with an integrated luminosity of ℒ = 2.5 ab ^-1 and at √(s) = 3 TeV with ℒ = 5 ab ^-1 . Combining e^+e^-→HHνν̅ and ZHH cross-section measurements at 1.4 TeV with differential measurements in e^+e^-→HHνν̅ events at 3 TeV, CLIC will be able to measure the trilinear Higgs self-coupling with a relative uncertainty of -8% and +11% at 68