  We report the observation of negative nonlocal resistances in multiterminal
mesoscopic gold Hall bar structures whose characteristic dimensions are larger
than the electron mean-free path. Our results can only be partially explained
by a classical diffusive model of the nonlocal transport, and are not
consistent with a recently proposed model based on spin Hall effects. Instead,
our analysis suggests that a quasiballistic transport mechanism is responsible
for the observed negative nonlocal resistance. Based on the sensitivity of our
measurements and the spin Hall effect model, we find an upper limit for the
spin Hall angle in gold of 0.022 at 4.5 K.
