Helicity Asymmetries in γd → ppπ- Rescattering Events

The strong force is one of the fundamental forces of nature, yet many of its features are still not yet well understood. We learn about it by investigating the interactions between various hadrons. One method to study how shortly-living hadrons interact with nucleons is via final-state interactions, where a hadron produced by a beam incident on a nucleon in a nucleus scatters off another nucleon. By measuring hadro-production off a deuteron target, information about the second interaction is gained. In this project, we analyzed data collected in the E06-103 experiment at Jefferson Lab, where a circularly-polarized photon beam was incident on a deuteron target. Our objective is to extract the beam-helicity asymmetry of the γd→ppπ- reaction and establish how it depends on kinematics. To maximize sensitivity to pπ- and pp final-state interactions, we select an event sample where both protons carry high momenta. We observe large helicity asymmetries for specific energies and angles of scattered particles. Here we discuss how these can be used to identify kinematics where specific final-state scatterings dominate. The methods we developed will be applied to the study of hyperon and J/psi final-state interactions.