Photo- and Electro-excitation of Bound Neutrons and Protons

Abstract

Data for pion photo-productions off the neutron ($\gamma n\to \pi N$) have been primarily extracted from deuteron-target data ($\gamma d\to \pi NN$) by applying kinematical cuts thereby isolating the quasi-free samples. We critically examine if the neutron-target data obtained through this conventional procedure can be contaminated by final state interactions (FSI) and/or the kinematical cuts. The analysis is conducted with a theoretical model for $\gamma d\to \pi NN$ that takes account of the impulse mechanisms supplemented by the $NN$ and $\pi N$ rescattering mechanisms. We show that the FSI effects still visibly remain in the extracted $\gamma$`$n$'$\to\pi N$ unpolarized cross sections and polarization asymmetries $E$ even after the kinematical cuts are applied. We also find the FSI effects on $\gamma$`$n$'$\to\pi^0n$ can be somewhat different from those on $\gamma$`$p$'$\to\pi^0p$.