Double-pion electroproduction off protons in deuterium: measurements of quasi-free cross sections and study of final state interactions

Exclusive reactions of meson photo- and electroproduction off protons are a very powerful tool to investigate the nucleon structure and the principles of strong interaction. Among them, the production of pion pairs plays a particularly important role: the channel contributes significantly to the total inclusive cross section for W ≤ 1.6 GeV and starts to dominate all other exclusive channels for W ≥ 1.6 GeV.

By now exclusive reactions off free protons have been studied in considerable detail, while experimental information on reactions occurring off nuclei is scarce and mostly limited to inclusive measurements. This situation causes a strong demand for exclusive measurements off bound nucleons, and the deuteron, being the lightest and weakly-bound nucleus, is the best target for initiating these efforts.

This talk will present the quasi-free cross sections for the process of charged double-pion electroproduction off protons bound in deuterium extracted in the second resonance region with the CLAS detector. In the talk, I will introduce the details of the cross section measurements and also focus on the analysis specificities caused by the Fermi motion of the initial proton and complex effects of the final state interactions between the reaction final hadrons and spectator neutrons.