The first measurement of the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(γ→,p)X using linearly polarized photons is reported. Cross sections and beam-polarization asymmetries for ${\mathrm{\theta }}_{\mathit{p}}^{\mathrm{lab}}$=60°–100° and ${\mathit{E}}_{\gamma }$=195–304 MeV are compared with a microscopic calculation which includes one-, two-, and three-nucleon absorption mechanisms. One- and two-nucleon absorption alone fails to describe the data at low proton momenta. The inclusion of three-nucleon absorption significantly improves the comparison with the measured cross sections. However, some features of the asymmetry distributions are not explained.

• Received 9 August 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.617