Mott-Schwinger Scattering of Polarized Cold and Thermal Neutrons

Abstract The availability of new, high intensity, cold and thermal neutron sources has opened the possibility to perform high precision fundamental neutron physics experiments, including measurements that study the hadronic weak interaction and standard model test measurements, using neutron beta decay. The observables in these experiments are usually correlated with the direction of neutron polarization and are often very small (10−8 → 10−6). Mott-Schwinger scattering of polarized neutrons can produce spin dependent beam steering which has the potential to produce significant systematic effects for these experiments. An accurate calculation of this process for neutral atoms and basic molecules has not been carried out for low energy neutrons. In this work, we derive a general expression for the electromagnetic (Mott-Schwinger) contributions to the analyzing power for low-energy neutron scattering. We obtain numerical results for 11 nuclei in the range of A = 1 to A = 208 and provide a series of graphs for easy reference and interpolation between A values. We also estimate the contribution of spin-dependent nucleon-nucleon forces and apply our results to determine the analyzing power of parahydrogen. Numerical calculations are performed to determine the analyzing power for the parahydrogen molecule and are compared to results obtained using analytical expressions.