Kaons and antikaons in asymmetric nuclear matter

The properties of kaons and antikaons and their modifications in isospin asymmetric nuclear matter are investigated using a chiral SU(3) model. These isospin-dependent medium effects are important for asymmetric heavy-ion collision experiments and will be especially relevant for the neutron-rich heavy-ion collision experiments in the future accelerator facility GSI Facility for Antiproton and Ion Research (GSI-FAIR). In the present work, the medium modifications of the energies of the kaons and antikaons, within the asymmetric nuclear matter, arise because of the interactions of kaons and antikaons with the nucleons and scalar mesons. The values of the parameters in the model are obtained by fitting the saturation properties of nuclear matter and kaon-nucleon scattering lengths for $I=0$ and $I=1$ channels. Furthermore, the isovector and isoscalar pion-nucleon scattering lengths are calculated within the chiral effective model and compared with earlier results from the literature. The kaon-nucleon and pion-nucleon $\Sigma$ coefficients are also calculated within the present chiral SU(3) model.

Figure 1

The symmetry energy, $a_4$, plotted as a function of the baryon density, ${\rho }_B/{\rho }_0$.

Figure 2

The kaon energies [for $K^{+}$ in (a) and for $K^0$ in (b)] in MeV plotted as functions of the baryon density, ${\rho }_B/{\rho }_0$, for different values of the isospin asymmetry parameter, $\eta =\frac{1}{2}({\rho }_n-{\rho }_p)/{\rho }_B$.

Figure 3

The energies of the antikaons [for $K^{-}$ in (a) and for $\overline{K^0}$ in (b)], at zero momentum as functions of the baryon density (${\rho }_B/{\rho }_0$), are plotted for different values of the isospin asymmetry parameter, $\eta$.

Figure 4

The kaon energies [for $K^{+}$ in (a), (c), and (e) and for $K^0$ in (b), (d), and (f)], as compared to the isospin symmetric case, plotted as functions of the momentum for various values of the baryon density, ${\rho }_B$, and for different values of the isospin asymmetry parameter, $\eta$.

Figure 5

The antikaon energies [for $K^{-}$ in (a), (c), and (e) and for $\overline{K^0}$ in (b), (d), and (f)], as compared to the isospin symmetric case, plotted as functions of the momentum for different values of the isospin asymmetry parameter, $\eta$, and for various values of the baryon density, ${\rho }_B$.

Figure 6

The kaon optical potentials [for $K^{+}$ in (a), (c), and (e) and for $K^0$ in (b), (d), and (f)] in MeV, plotted as functions of the momentum for various baryon densities, ${\rho }_B$, and for different values of the isospin asymmetry parameter, $\eta$.

Figure 7

The antikaon optical potentials [for $K^{-}$ in (a), (c), and (e) and for $\overline{K^0}$ in (b), (d), and (f)] in MeV, plotted as functions of the momentum for various baryon densities, ${\rho }_B$, and for different values of the isospin asymmetry parameter, $\eta$.