This document is meant to provide semi-quantitative arguments to evaluate the
luminosity needed at ILC to achieve a precise measurement of the Higgs mass,
width and invisible decays. It is shown that for mH=120 GeV, one can save an
order of magnitude on the luminosity needed to achieve a given precision on the
Higgs mass, as compared to what can be obtained at \sqrt s=350 GeV, by running
near threshold. Since the recoil mass resolution near threshold is independent
of the Higgs mass, one can also access the Higgs width for masses above 170
GeV. This strategy of running just above threshold is also optimal to measure
or set upper limits on the Higgs invisible branching ratio. Two MSSM scenarios
are presented to illustrate the potential interest of an optimized recoil mass
resolution. A simplified description of the various experimental mechanisms
affecting this type of measurement is presented: detector resolution for
leptons and jets, luminosity and beamstrahlung energy dependence, initial and
final radiation of the involved leptons.Comment: Work presented at the International Collider Physics and Detector,
ECFA Workshop, Valencia, Spain, November 7-10, 200
