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 E-sym(rho). 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 E-sym(kin) (rho 0) = -16.94 +/- 13.66MeV which is dramatically different from the prediction of E-sym(kin) (rho 0) +/- 12.5 MeV by FFG models at nuclear matter saturation density rho 0 = 0.16 fm(-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 rho 0, the SRC-modified single-nucleon momentum distribution is found to make the E-sym(rho) more concave around rho 0 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.