(Triple) Higgs-coupling imprints at future lepton colliders

The measurement of the triple Higgs coupling is one of the major goals of the future colliders. The direct measurement at lepton colliders relies on the production of Higgs boson pairs in two main channels, e +e − → ZHH which is dominant at centre-of-mass energies below 1 TeV and maximal at around 500 GeV, and e +e − → HHνeν¯e that becomes dominant for high-energy colliders. This direct measurement requires to be at least at a centre-of-mass energy of 500 GeV, and is hence only possible at future linear colliders such as the International Linear Collider (ILC) operating at 500 GeV or 1 TeV [1], or the Compact LInear Collider (CLIC) operating at 1.4 TeV (stage 2) or 3 TeV (stage 3) [2]. The SM triple Higgs coupling sensitivity is estimated to be δκλ = (λHHH/λSM HHH − 1) ∼ 28% at the 500 GeV ILC with a luminosity of 4 ab−1 [3, 4] and δκλ ∼ 13% at the CLIC when combining the 1.4 TeV run with 2.5 ab−1 of data and the 3 TeV run with 5 ab−1 of data [5].