Electromagnetic structure of strange vector mesons in nuclear medium

Abstract

We investigate the in-medium modifications of the charge (electric) $G_C^{\ast }(Q^2)$, magnetic $G_M^{\ast }(Q^2)$, and quadrupole $G_Q^{\ast }(Q^2)$ form factors of the positively charged vector meson $K^{\ast +}$ in symmetric nuclear matter at zero temperature within the Schwinger proper-time Nambu-Jona-Lasinio (NJL) model. In this framework, both the nuclear medium effects and the electromagnetic structure of the $K^{\ast +}$ meson are described consistently in the NJL model at the quark level. We find that the charge, magnetic, and quadrupole form factors are suppressed with increasing nuclear density, indicating substantial in-medium modifications of the strange vector meson's internal structure. We further obtain a charge radius of $r_{K^{\ast +}}^{\ast }=0.74\mathrm{fm}$ at normal nuclear density, which is slightly smaller than the corresponding value for the ${\rho }^{+}$ meson, $r_{{\rho }^{+}}^{\ast }\simeq 0.75\mathrm{fm}$.

Comments: 13 pages, 8 figures, 1 table