Open Charm mesons in magnetized nuclear matter -- effects of (inverse) magnetic catalysis

Abstract: The in-medium masses of the open charm ($D$ and $\bar D$) mesons in magnetized isospin asymmetric nuclear matter are investigated within a chiral effective model, including the contributions of the Dirac sea (DS) to the self-energies of the nucleons. Within the model, the masses of these mesons are calculated from their interactions with the nucleons and the scalar ($\sigma\sim(\langle\bar u u\rangle+\langle \bar d d \rangle)$, $\zeta\sim\langle {\bar s}s\rangle$ and $\delta\sim(\langle{\bar u} u\rangle-\langle {\bar d} d\rangle)$) fields. The Dirac sea contributions are observed to lead to an enhancement (reduction) of the quark condensates with increase in magnetic field, an effect called `(inverse) magnetic catalysis'. These contributions are observed to appreciably modify the open charm meson masses calculated within the chiral effective model. In the presence of an external magnetic field, there is mixing of the pseudoscalar and the vector mesons (PV mixing), leading to as a drop (increase) in the mass of the pseudoscalar (longitudinal component of the vector) meson. The effects of the (inverse) magnetic catalysis, in addition to the PV mixing and Landau level contribtuions (for charged mesons) are observed to lead to significant modifications to the masses of the open charm mesons. These can modify the decay widths of the charmonium states to open charm mesons, e.g., $\psi(3770)\rightarrow D\bar D$, as well as $D^*\rightarrow D\pi$ (and $\bar {D^*}\rightarrow {\bar D}\pi$), which can affect the production of the open charm and charmonium states in ultra relativistic peripheral heavy ion collision experiments, where the created magnetic field is huge.