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

TL;DR

This study investigates the spin dependence of a specific neutron-induced p-wave resonance in La-139, revealing enhanced parity violation and providing data for understanding symmetry violations in nuclear reactions.

Contribution

It presents the first measurement of spin dependence in the p-wave resonance of La-139 plus neutron using polarized beams and targets, highlighting the parity violation effects.

Findings

Enhanced parity violation observed at 0.75 eV resonance

Partial neutron width determined from spin dependence measurements

Provides data for studying symmetry violation effects in nuclei

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.