Studies of Final-State Interactions via Helicity Asymmetries in Exclusive Pseudoscalar Meson Photoproduction off Deuteron

Exclusive meson photoproduction off deuteron is a great tool to study final-state interactions (FSI) between the hadrons produced in the scattering of the incident photon off one of the target nucleons and the spectator nucleon. FSI in the reaction $\gamma d\to K^{+}\Lambda n$ enable access the dynamics of $\Lambda n$ elastic scattering and provide a method of studying the hyperon-nucleon interaction. Also, as deuteron is often used as a neutron target, FSI in reactions such as $\gamma d\to p\pi^{+}\pi^{-}$ contribute to the reaction dynamics in addition to the quasi-free $\gamma n\to p\pi^{-}$ and their understanding is critical for the estimate of observables off the free nucleon. In this talk we will show preliminary results for beam-helicity asymmetries for the reactions $\vec{{\gamma }}d\to K^{+}\Lambda n$ , $\vec{{\gamma }}d\to pp\pi^{-}$ , and $\vec{{\gamma }}d\to p\pi^{+}\pi^{-}n$ and their evolution over the spectator-nucleon virtuality. The data were obtained with the CLAS at Jefferson Lab in experiment E06-103 where a circularly-polarized photon beam with energies between 0.5 GeV and 2.5 GeV was incident on unpolarized deuteron target. We will present an interpretation of our $K^{+}\Lambda n$ results in terms of $\Lambda n$ elastic scattering. We will also discuss the extraction of polarization observables for photoproduction off the free nucleon using our helicity asymmetries for reactions off the deuteron.