  We measured fragmentation cross sections produced using the primary beam of
$^{86}$Kr at 64 MeV/nucleon on $^9$Be and $^{181}$Ta targets. The cross
sections were obtained by integrating the momentum distributions of isotopes
with 25<Z<36 measured using the RIPS fragment separator at RIKEN. The
cross-section ratios obtained with the $^{181}$Ta and $^{9}$Be targets depend
on the fragment masses, contrary to the simple geometrical models. We compared
the extracted cross sections to EPAX; an empirical parameterization of
fragmentation cross sections. Predictions from current EPAX parameterization
severely overestimate the production cross sections of very neutron-rich
isotopes. Attempts to obtain another set of EPAX parameters specific to the
reaction studied here, to extrapolate the neutron-rich nuclei more accurately
have not been very successful, suggesting that accurate predictions of
production cross sections of nuclei far from the valley of stability require
information of nuclear properties which are not present in EPAX.
