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+eββhZ), such a collider would measure
weak boson pair production (e+eββWW) with an astonishing precision. The
weak-boson-fusion production process (e+eββΞ½Ξ½Λh) provides an
increasingly powerful handle at higher center-of-mass energies. High energies
also benefit the associated top-Higgs production (e+eββttΛh) 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.Comment: 55 pages, lots of figures, v2: references added, minor corrections,
extended discussions on quadratic EFT contributions and beam polarization
effects, matches published version in JHE