Angular Distribution of $\gamma$-rays from Neutron-Induced Compound States of ${}^{140}$La

Abstract

Angular distribution of individual $\gamma$-rays, emitted from a neutron-induced compound nuclear state via radiative capture reaction of ${}^{139}$La(n,$\gamma$) has been studied as a function of incident neutron energy in the epithermal region by using germanium detectors. An asymmetry $A_{\mathrm{LH}}$ was defined as $(N_{\mathrm{L}}-N_{\mathrm{H}})/(N_{\mathrm{L}}+N_{\mathrm{H}})$, where $N_{\mathrm{L}}$ and $N_{\mathrm{H}}$ are integrals of low and high energy region of a neutron resonance respectively, and we found that $A_{\mathrm{LH}}$ has the angular dependence of $(A\cos {\theta }_{\gamma }+B)$, where ${\theta }_{\gamma }$ is emitted angle of $\gamma$-rays, with $A=-0.3881\pm 0.0236$ and $B=-0.0747\pm 0.0105$ in 0.74 eV p-wave resonance. This angular distribution was analyzed within the framework of interference between s- and p-wave amplitudes in the entrance channel to the compound nuclear state, and it is interpreted as the value of the partial p-wave neutron width corresponding to the total angular momentum of the incident neutron combined with the weak matrix element, in the context of the mechanism of enhanced parity-violating effects. Additionally we used the result to quantify the possible enhancement of the breaking of the time-reversal invariance in the vicinity of the p-wave resonance.

arXiv comment14pages, 25 figures

References in corpus (4)

• Matrix Elements between Nuclear Compound States and Dynamical Enhancement of the Weak Interaction
• The 139La(n,gamma) cross section: key for the onset of the s process
• Nuclear spin dependence of time reversal invariance violating effects in neutron scattering
• Effects of T- and P-odd weak nucleon interaction in nuclei: renormalizations due to residual strong interaction, matrix elements between compound states and their correlations with P-violating matrix elements

Cited by in corpus (12)

• Transverse asymmetry of $\gamma$ rays from neutron-induced compound states of ${}^{140}\mathrm{La}$
• Time reversal invariance violation in neutron-nucleus scattering
• Measurement of the transverse asymmetry of $\gamma$-rays in the ${}^{117}$Sn(n,$\gamma$)${}^{118}$Sn reaction
• Nuclear spin dependence of time reversal invariance violating effects in neutron scattering
• Energy dependent angular distribution of individual $\gamma$-rays in the ${}^{139}$La($n$, $\gamma$)${}^{140}$La* reaction
• Angular distribution of $\gamma$ rays from the p-wave resonance of ${}^{118}$Sn
• Angular distribution of $\gamma$-rays from a neutron-induced $p$-wave resonance of ${}^{132}$Xe
• High sensitivity of a future search for P-odd/T-odd interactions on the 0.75 eV $p$-wave resonance in $\vec{n}{+}^{139}\overrightarrow{\mathrm{La}}$ forward transmission determined using pulsed neutron beam
• A modular apparatus for use in high-precision measurements of parity violation in polarized eV neutron transmission`
• Measurements of neutron total and capture cross sections of ${}^{139}$La and evaluation of resonance parameters
• Parity and Time Reversal Invariance Violation in Neutron-Nucleus Scattering
• Measurement of nuclear spin relaxation time in lanthanum aluminate for development of polarized lanthanum target