Transverse asymmetry of individual ${\hat{I}}^3$-rays in the ${}^{139}$La($\vec{n}$, ${\hat{I}}^3$)${}^{140}$La reaction

Abstract

The enhancement of the parity-violating asymmetry in the vicinity of $p$-wave compound nuclear resonances was observed for a variety of medium-heavy nuclei. The enhanced parity-violating asymmetry can be understood using the $s$-$p$ mixing model. The $s$-$p$ mixing model predicts several neutron energy-dependent angular correlations between the neutron momentum ${\vec{k}}_n$, neutron spin $\vec{\ddot{I}}{ƒ}_n$, ${\hat{I}}^3$-ray momentum ${\vec{k}}_{\hat{I}}^3$, and ${\hat{I}}^3$-ray polarization $\vec{\ddot{I}}{ƒ}_{\hat{I}}^3$ in the $(n,{\hat{I}}^3)$ reaction. In this paper, the improved value of the transverse asymmetry of ${\hat{I}}^3$-ray emissions, corresponding to a correlation term $\vec{\ddot{I}}{ƒ}_n\cdot ({\vec{k}}_n\times {\vec{k}}_{\hat{I}}^3)$ in the ${}^{139}\mathrm{La}(\vec{n},{\hat{I}}^3{)}^{140}\mathrm{La}$ reaction, and the transverse asymmetries in the transitions to several low excited states of ${}^{140}\mathrm{La}$ are reported.

5 pages, 5 figures, 2 tables