Quasifree pion electroproduction from nuclei in theΔregion

Abstract

We present calculations of the reaction ${A(e,e}^{\ensuremath{'}}\ensuremath{\pi}N)B$ in the distorted (and plane) wave impulse approximation. The reaction allows for the study of the production process in the nuclear medium without being obscured by the details of nuclear transition densities. First, a pion electroproduction operator suitable for nuclear calculations is obtained by extending the Blomqvist-Laget photoproduction operator to the virtual photon case, which describes the existing data reasonably well. It is applied in nuclei to predict nuclear cross sections under a variety of kinematic arrangements. Issues such as the effects of the interference of the $\ensuremath{\Delta}$ resonance with the background, sensitivities to the quadrupole component of the $\ensuremath{\Delta}$ excitation and to the electromagnetic form factors, and the role of final-state interactions are studied in detail. It is found that the longitudinal and the LT interference structure functions in ${(e,e}^{\ensuremath{'}}{\ensuremath{\pi}}^{0}N)$ are sufficiently sensitive to extract medium modifications of the $\ensuremath{\Delta}$ quadrupole component. Methods on how to experimentally separate the various pieces in the coincidence cross section are suggested. Finally, the model is compared to a recent SLAC experiment.