Measurement of longitudinal asymmetry in neutron radiative capture reactions

Abstract The helicity dependence was measured in neutron radiative capture reactions for various nuclei using a polarized low-energy neutron beam. The neutron spin was polarized upon passing through a dynamically polarized proton filter. The neutron polarization was around 72%. The value of the asymmetry A L in the p-wave resonance of 139 La at 0.734 eV was (9.4 ± 0.4)%. Measurements were also carried out for 138 La, 98 Mo, 103 Pd and 129 Xe. For the resonance of 138 La at 2.99 eV, A L = (0.37 ± 0.22)%. For the p-wave resonance of 108 Pd at 2.96 eV, A L = −(0.30 ± 0.18)%. For the p-wave resonance of 98 Mo at 12.1 eV and the resonance of 129 Xe at 9.5 eV, preliminary values of the asymmetry A L were smaller than 0.4% and 1%, respectively.