Seminarium "High Energy, Cosmology and Astro-particle Physics (HECA)"

In this talk we present a picture of what life is like at a multi-TeV muon collider. We start by showing that beyond a few TeV electroweak (EW) boson fusion/scattering becomes the dominant production vehicle at lepton colliders for both the Standard Model and new physics. Motivated by this, we revisit the treatment of weak gauge bosons as constituents of high-energy leptons. In particular, using a new, public implementation of (polarized) W/Z parton distribution functions in the Monte Carlo event generator MadGraph5_aMC@NLO, we report the size of universal, i.e., process independent, corrections that spoil the accuracy of a (factorized) scattering formula for muon colliders. Guided by this insight, we give an outlook for polarized EW boson scattering at many TeVs.