Spectral function for $\bar{D}_{0}^{\ast}$ $(0^+)$ meson in isospin asymmetric nuclear matter with chiral partner structure
We study a spectral function for $\bar{D}_0^*$ $(0^+)$ meson in symmetric and neutron-rich asymmetric nuclear matter from the viewpoint of the partial restoration of chiral symmetry. Nuclear matter is constructed by a parity doublet model with hidden local symmetry which can reproduce properties at normal nuclear matter density as well as those in the vacuum. $\bar{D}$ mesons are introduced by the chiral partner structure. Our results show that a mass of $\bar{D}$ ($0^-$) meson increases while a mass of $\bar{D}_0^*$ meson decreases at mean field level as we increase the baryon density, reflecting the partial restoration of chiral symmetry. In the spectral function for $\bar{D}_0^*$ meson, we find a threshold enhancement is remarkably enhanced which indicates this peak is an appropriate probe to observe the partial restoration of chiral symmetry in nuclear matter. We also find a resonance of $\bar{D}_0^*$ meson revives at higher density due to a narrowing of the phase space. In the spectral function in neutron-rich asymmetric nuclear matter, we observe the threshold enhancement in negatively-charged $\bar{D}_0^*$ meson channel stands at higher energy and its height is more enhanced compared to neutral $\bar{D}_0^*$ meson channel, due to the violation of isospin symmetry. On the other hand, the resonance of negatively-charged $\bar{D}_0^*$ meson is slightly suppressed compared to the neutral one.