Delineating effects of tensor force on the density dependence of nuclear symmetry energy

TL;DR

This paper investigates how the tensor force influences the density dependence of nuclear symmetry energy, revealing that high momentum tails significantly reduce the kinetic part and can even make it negative, with implications for nuclear physics models.

Contribution

The study demonstrates the impact of tensor force on the kinetic symmetry energy and quantifies the high momentum tail effects using phenomenological models and recent experimental data.

Findings

High momentum tail reduces kinetic symmetry energy below Fermi gas predictions.

Approximately 15% nucleons in high momentum tail makes kinetic symmetry energy negligible.

Tensor force effects confirmed by independent microscopic nuclear many-body studies.

Abstract

In this talk, we report results of our recent studies to delineate effects of the tensor force on the density dependence of nuclear symmetry energy within phenomenological models. The tensor force active in the isosinglet neutron-proton interaction channel leads to appreciable depletion/population of nucleons below/above the Fermi surface in the single-nucleon momentum distribution in cold symmetric nuclear matter (SNM). We found that as a consequence of the high momentum tail in SNM the kinetic part of the symmetry energy $E^{kin}_{sym}(\rho)$ is significantly below the well-known Fermi gas model prediction of approximately $12.5 (\rho/\rho_0)^{2/3}$. With about 15% nucleons in the high momentum tail as indicated by the recent experiments at J-Lab by the CLAS Collaboration, the $E^{kin}_{sym}(\rho)$ is negligibly small. It even becomes negative when more nucleons are in the high momentum tail in SNM. These features have recently been confirmed by three independent studies based on the state-of-the-art microscopic nuclear many-body theories. In addition, we also estimate the second-order tensor force contribution to the potential part of the symmetry energy. Implications of these findings in extracting information about nuclear symmetry energy from nuclear reactions are discussed briefly.