The availability of new, high-intensity, cold and thermal neutron sources has opened the possibility of performing 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 $({10}^{-8}\to {10}^{-6})$. Mott-Schwinger scattering of polarized neutrons can produce spin-dependent shifts in beam centroids, which has the potential to produce significant systematic effects for these types of experiments. An accurate calculation of this process for neutral atoms and basic molecules has not been carried out for low neutron energies. 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.

• Received 17 June 2008

DOI:https://doi.org/10.1103/PhysRevC.78.044003