Paper detail

Spin Polarization in $γd \to \vec{n}p$ at Low Energies with a Pionless Effective Field Theory

With the use of pionless effective field theory including dibaryon fields, we study the $γd \to \vec{n} p$ reaction for the laboratory photon energy $E_γ^{lab}$ ranging from threshold to 30 MeV. Our main goal is to calculate the neutron polarization $P_{y'}$ defined as $P_{y'} = (σ_+ - σ_-)/(σ_+ + σ_-)$, where $σ_+$ and $σ_-$ are the differential cross sections for the spin-up and spin-down neutrons, respectively, along the axis perpendicular to the reaction plane. We also calculate the total cross section as well as the differential cross section $σ(θ)$, where $θ$ is the colatitude angle. Although the results for the total and differential cross sections are found to agree reasonably well with the data, the results for $P_{y'}$ show significant discrepancy with the experiment. We comment on this discrepancy.