  Experimental information on fragment emissions is important in understanding
the dynamics of nuclear collisions and in the development of transport model
simulating heavy-ion collisions. The composition of complex fragments emitted
in the heavy-ion collisions can be explained by statistical models, which
assume that thermal equilibrium is achieved at collision energies below 100
MeV/u. Our new experimental data together with theoretical analyses for light
particles from Sn+Sn collisions at 270 MeV/u, suggest that the hypothesis of
thermal equilibrium breaks down for particles emitted with high transfer
momentum. To inspect the system's properties in such limit, the scaling
features of the yield ratios of particles from two systems, a neutron-rich
system of ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ and a nearly symmetric
system of ${}^{108}\mathrm{Sn}+{}^{112}\mathrm{Sn}$, are examined in the
framework of the statistical multifragmentation model and the antisymmetrized
molecular dynamics model. The isoscaling from low energy particles agree with
both models. However the observed breakdown of isoscaling for particles with
high transverse momentum cannot be explained by the antisymmetrized molecular
dynamics model.
