LCPs (bottom). The vertical line in the bottom panel represent the energy limit above which $DR(N/Z)$ of LCPs becomes more or less insensitive. Solid and open circles represent the soft and stiff symmetry energies, respectively. The solid, dashed, and dot-dashed line corresponds to double ratios from $^{132}$Sn + $^{132}$Sn to $^{124}$Sn + $^{124}$Sn, $^{124}$Sn + $^{124}$Sn to $^{112}$Sn + $^{112}$Sn, and $^{132}$Sn + $^{132}$Sn to $^{112}$Sn + $^{112}$Sn, respectively. ](figure7.eps){width="90mm"}

![\[fig:8\] Isospin asymmetry dependence of the double neutron-to-proton ratio from free nucleons at different incident energies. The different symbols have the same meaning as in Fig. \[fig:5\]. ](figure8.eps){width="90mm"}

![\[fig:9\] Incident energy dependence of the power-law exponent $\tau$ from Fig. \[fig:8\]. The symbols and lines are the same as in Figs. 5 and 8.](figure9.eps){width="90mm"}

Incident energy and isospin asymmetry dependencies of double neutron to proton ratio
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In order to cancel the Coulomb effects and to see the effect of symmetry energy, we show in Fig. \[fig:7\], the incident energy dependence of the double ratio from different isotopes of Sn with different combinations, namely, $^{132}$Sn + $^{132}$Sn and $^{124}$Sn + $^{124}$Sn, $^{124}$Sn + $^{124}$Sn and $^{112}$Sn + $^{112}$Sn, $^{132}$Sn + $^{132}$Sn and $^{112}$Sn + $^{112}$Sn, having differences of 8, 12, and 