Efficiency corrected single ratios of neutron and proton spectra in central $^{ 112}$Sn+$^{ 112}$Sn and $^{ 124}$Sn+$^{ 124}$Sn collisions at 120 MeV/u are combined with double ratios to provide constraints on the density and momentum dependencies of the isovector mean-field potential. Bayesian analyses of these data reveal that the isoscalar and isovector nucleon effective masses, $m_s^* - m_v^*$ are strongly correlated. The linear correlation observed in $m_s^* - m_v^*$ yields a nearly independent constraint on the effective mass splitting $\Delta m_{ np}^*= (m_n^*-m_p^*)/m_N = -0.05_{ -0.09}^{ +0.09}\delta$. The correlated constraint on the standard symmetry energy, $S_0$ and the slope, $L$ at saturation density yields the values of symmetry energy $S(\rho_s)=16.8_{ -1.2}^{ +1.2}$ MeV at a sensitive density of $\rho_s/\rho_0 = 0.43_{ -0.05}^{ +0.05}$.
Categories: nucl-ex nucl-th