Precision study of electroweak symmetry breaking strongly motivates the construction of a lepton collider with center-of-mass energy of at least 240 GeV. Besides Higgsstrahlung (e + e − → hZ), such a collider would measure weak boson pair production (e + e − → W W ) with an astonishing precision. The weak-boson-fusion production process (e + e − → ννh) provides an increasingly powerful handle at higher center-of-mass energies. High energies also benefit the associated top-Higgs production (e + e − → tth) that is crucial to constrain directly the top Yukawa coupling. The impact and complementarity of differential measurements, at different center-of-mass energies and for several beam polarization configurations, are studied in a global effective-field-theory framework. We define a global determinant parameter (GDP) which characterizes the overall strengthening of constraints independently of the choice of operator basis. The reach of the CEPC, CLIC, FCC-ee, and ILC designs is assessed.

Vector boson fusion processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. A feasibility study for the search of supersymmetric dark matter in the final state of two vector boson fusion jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of wino and bino-Higgsino dark matter. The LHC could probe wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000  fb(-1).