LAUSR

From a Bayesian analysis of the electric dipole polarizability, the constrained energy of isovector giant dipole resonance, the peak energy of isocalar giant quadrupole resonance and the constrained energy of isocalar giant monopole resonance in Pb, we extract the isoscalar and isovector effective masses in nuclear matter at saturation density ρ0 as m ∗ s,0/m = 0.87 +0.04 −0.04 and m ∗ v,0/m = 0.78 +0.06 −0.05 at 90% confidence level. The obtained constraints on ms,0 and m ∗ v,0 lead to a positive isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry δ at ρ0 as m ∗ n−p/m = (0.20 −0.14)δ. In addition, the symmetry energy at the subsaturation density ρ ∗ = 0.05 fm−3 is determined to be Esym(ρ ∗) = 16.7 ± 1.3 MeV at 90% confidence level.