Broadening of ρ(→ e+e-) meson produced coherently in the photonuclear reaction

The e+e- invariant mass distribution spectra are calculated to estimate the hadron parameters of the ρ meson produced coherently in the photonuclear reaction. The elementary reaction occurring in the nucleus is considered to proceed as γN → ρ 0 N; ρ 0 → e e+e-. We describe the elementary ρ meson photoproduction by the experimentally determined reaction amplitude fγN→ρ0N. The ρ meson propagator is presented by the eikonal form, and the ρ meson nucleus optical potential VOρ appearing in it is estimated using the ''t ρ'' approximation. The ρ meson nucleon scattering amplitude fρN extracted from the measurements is used to generate this potential. The calculated e+e- invariant mass distribution spectra are compared with those measured at Jefferson Laboratory. The calculated results for the transparency ratio are also presented. (orig.)