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

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 ${\vec{\sigma }}_n$, $\gamma$-ray momentum ${\vec{k}}_{\gamma }$, and $\gamma$-ray polarization ${\vec{\sigma }}_{\gamma }$ in the $(n,\gamma )$ reaction. In this paper, the improved value of the transverse asymmetry of $\gamma$-ray emissions, corresponding to a correlation term ${\vec{\sigma }}_n\cdot ({\vec{k}}_n\times {\vec{k}}_{\gamma })$ in the ${}^{139}\mathrm{L}\mathrm{a}(\vec{n},\gamma {)}^{140}\mathrm{L}\mathrm{a}$ reaction, and the transverse asymmetries in the transitions to several low excited states of ${}^{140}\mathrm{L}\mathrm{a}$ are reported.