The Higgs decay width can also be obtained from the ratio of rate products, σHνeνe B(H → bb ̄)× σ2HZ to σZH B(H → bb ̄) × σZH B(H → WW∗). The first of these four rates is determined from counting WW-fusion-to-Higgs events in the bbνeνe final state. This final state is contaminated by several background processes, of which e+e− → γ∗Z, e+e− → ZZ, and e+e− → HZ, with Z → νν ̄. The discrimination between these backgrounds and the signal mostly stems the visible invariant mass (which equals the Higgs boson mass for the signal, but also for the e+e− → HZ background), and the missing mass (which equals the Z mass for the e+e− → HZ background, but not for the signal).
The requirements on the detector design to achieve the visible and missing mass resolutions in a hadronic final state (taking into account the total energy and momentum conservation, as well as the mass constraints) necessary for a maximal separation between the signal and the backgrounds, and therefore an optimal determination of the Higgs boson width, will be studied at √s ∼ 365 GeV. The exercise will be repeated at ∼ 240 GeV, where the separation is less pronounced, and an optimization with respect to the centre-of-mass energy (towards smaller values) will be attempted.