Effect of in-medium parameters of rho meson in its photoproduction reactions on nuclei

There exist model calculations showing the modification of the hadronic parameters of $\rho$ meson in the nuclear environment. From these parameters, we extract the $\rho$ meson nucleus optical potential and show the medium effect due to this potential on the $\rho$ meson mass distribution spectra in the photonuclear reaction. The calculated results reproduced reasonably the measured $e^+e^-$ invariant mass, i.e., $\rho$ meson mass, distribution spectra in the $( \gamma, \rho^0 \to e^+e^- )$ reaction on nuclei.