  In this paper, we propose a dedicated forward detector, FOREHUNT (FORward
Experiment for HUNdred TeV), for 100 TeV FCC-hh for the detection of light
long-lived particles (LLP) coming from $B$-meson decay. We calculate the signal
acceptance as a function of mass and proper decay length of the LLP for 100 TeV
and interpret our result in terms of model parameters for models of dark Higgs
scalar and heavy neutral leptons. We also compare the sensitivity with proposed
transverse detectors like MATHUSLA, CODEX-b for HL-LHC, and DELIGHT (Detector
for long-lived particles at high energy of 100 TeV) for FCC-hh. Our analysis
reveals that if the LLP has low decay length < 10 m, a forward detector like
FOREHUNT is the best option to look for the decaying LLP, while DELIGHT is
preferable for higher decay lengths.
