  Within the theory of supersymmetry, the lightest neutralino is a dark matter
candidate and is often assumed to be the lightest supersymmetric particle (LSP)
as well. If the neutral wino or higgsino is dark matter, the upper limit of the
LSP mass is determined by the observed relic density of dark matter. If the LSP
is a nearly-pure neutral state of the wino or higgsino, the lightest chargino
state is expected to have a significant lifetime due to a tiny mass difference
between the LSP and the chargino. This article presents discovery potential of
the 100 TeV future circular hadron collider (FCC) for the wino and higgsino
dark matter using a disappearing-track signature. The search strategy to extend
the discovery reach to the thermal limits of wino/higgsino dark matter is
discussed with detailed studies on the background rate and the reference design
of the FCC-hadron detector under possible running scenarios of the FCC-hadron
machine. A proposal of modifying the detector layout and several ideas to
improve the sensitivity further are also discussed.
