  We report on a comparison study of the Monte Carlo packages GEANT4 and FLUKA
for simulating neutron production by muons penetrating deep underground. GEANT4
is found to generate fewer neutrons at muon energies above ~100 GeV, by at most
a factor of 2 in some materials, which we attribute mainly to lower neutron
production in hadronic cascades. As a practical case study, the muon-induced
neutron background expected in a 250 kg liquid-xenon WIMP dark matter detector
was calculated and good agreement was found for the recoil event rates. The
detailed model of neutron elastic scattering in GEANT4 was also shown to
influence the nuclear recoil spectrum observed in the target, which is
presently a shortcoming of FLUKA. We conclude that both packages are suited for
this type of simulation, although further improvements are desirable in both
cases.
