Spin dependence in the $p$-wave resonance of ${^{139}\vec{\rm{La}}+\vec{n}}$

Abstract

We measured the spin dependence in a neutron-induced $p$-wave resonance by using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75~eV $p$-wave resonance state of $^{139}$La+$n$, where largely enhanced parity violation has been observed. We determined the partial neutron width of the $p$-wave resonance by measuring the spin dependence of the neutron absorption cross section between polarized $^{139}\rm{La}$ and polarized neutrons. Our findings serve as a foundation for the quantitative study of the enhancement effect of the discrete symmetry violations caused by mixing between partial amplitudes in the compound nuclei