Measuring Higgs couplings at a linear collider (Vol. 44 No. 3)

In 2012 the experiments ATLAS and CMS discovered a new particle in proton-proton collisions at CERN's Large Hadron Collider (LHC). The measurements show that the properties of the particle are compatible with those predicted for the Higgs boson of the Standard Model. In the article we estimate the precision with which some of the fundamental properties of the particle, its couplings to other particles, can be measured including theoretical errors, at a high-luminosity LHC (HL-LHC), a linear electron-positron collider and the combination of the two. The uncertainties are expected to be better than 1% for a single parameter modifying all Higgs couplings simultaneously, and at the percent level if all relevant couplings are left free and independent of each other. The combination of the measurements at the two machines improves on the uncertainty of each one of these. Thus a HL-LHC and a linear collider form a dream team to study the properties of the Higgs boson with high precision.