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 → ρ0N; ρ0 → e+e−. We describe the elementary ρ meson photoproduction by the experimentally determined reaction amplitude $$f_{\gamma {\rm N} \to \rho ^0 {\rm N}}$$. 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 “tϱ” 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.