Symmetry energy of cold nucleonic matter within a relativistic mean field model encapsulating effects of high-momentum nucleons induced by short-range correlations

It is well known that short-range nucleon-nucleon correlations (SRC) from the tensor components and/or the repulsive core of nuclear forces lead to a high- (low-)momentum tail (depletion) in the single-nucleon momentum distribution above (below) the nucleon Fermi surface in cold nucleonic matter. Significant progress was made recently in constraining the isospin-dependent parameters characterizing the SRC-modified single-nucleon momentum distribution in neutron-rich nucleonic matter using both experimental data and microscopic model calculations. Using the constrained single-nucleon momentum distribution in a nonlinear relativistic mean field (RMF) model, we study the equation of state (EOS) of asymmetric nucleonic matter (ANM), especially the density dependence of nuclear symmetry energy Esym(ρ). First, as a test of the model, the average nucleon kinetic energy extracted recently from electron-nucleus scattering experiments using a neutron-proton dominance model is well reproduced by the RMF model incorporating effects of the SRC-induced high-momentum nucleons, while it is significantly under predicted by the RMF model using a step function for the single-nucleon momentum distribution as in free Fermi gas (FFG) models. Second, consistent with earlier findings within nonrelativistic models, the kinetic symmetry energy of quasinucleons is found to be Esymᵏⁱⁿ(ρ₀)=-16.94±13.660.16em0exMeV which is dramatically different from the prediction of Esymᵏⁱⁿ(ρ₀)≈12.5 MeV by FFG models at nuclear matter saturation density ρ₀=0.160.16em0exfm^-3. Third, comparing the RMF calculations with and without the high-momentum nucleons using two sets of model parameters both reproducing identically all empirical constraints on the EOS of symmetric nuclear matter (SNM) and the symmetry energy of ANM at ρ₀, the SRC-modified single-nucleon momentum distribution is found to make the Esym(ρ) more concave around ρ₀ by softening it significantly at both subsaturation and suprasaturation densities, leading to an isospin-dependent incompressibility of ANM in better agreement with existing experimental data. Fourth, the maximum mass of neutron stars is enhanced by the increased kinetic pressure from high-momentum nucleons at suprasaturation densities in SNM.