Electromagnetic structure of charged and neutral strange vector mesons

We investigate the electromagnetic form factors (EMFFs) of the charged $K^{*+}(892)$ ($u\bar{s}$) and neutral $K^{0}(896)$ ($d\bar{s}$) strange vector mesons within the covariant Nambu--Jona-Lasinio (NJL) model, employing the Schwinger proper-time regularization scheme to regularize ultraviolet divergences while incorporating the QCD aspect of quark confinement. To this end, we evaluate the charge (electric) $G_C(Q^2)$, magnetic $G_M(Q^2)$, and quadrupole $G_Q(Q^2)$ form factors, as well as the charge radii, of the charged $K^{+}(892)$ and neutral $K^{0}(896)$ strange vector mesons. We find the charge radii to be $\langle r^2 \rangle_{K^{+}} = 0.45~\mathrm{fm}^2$ and $\langle r^2 \rangle_{K^{0}} = -0.04~\mathrm{fm}^2$, respectively, while the corresponding magnetic moments are $\mu_{K^{+}} = 2.67,\mu_N$ and $\mu_{K^{*0}} = 0.032,\mu_N$. These results are consistent with other theoretical calculations and lattice QCD simulations.