TY - JOUR
T1 - Angular distribution of γ rays from neutron-induced compound states of la 140
AU - Okudaira, T.
AU - Takada, S.
AU - Hirota, K.
AU - Kimura, A.
AU - Kitaguchi, M.
AU - Koga, J.
AU - Nagamoto, K.
AU - Nakao, T.
AU - Okada, A.
AU - Sakai, K.
AU - Shimizu, H. M.
AU - Yamamoto, T.
AU - Yoshioka, T.
N1 - Funding Information:
The authors would like to thank the staff of ANNRI for the maintenance of the germanium detectors, and MLF and J-PARC for operating the accelerators and the neutron-production target. We would like to thank Dr. K. Kino for the calculation of the pulse shape of the neutron beam. We also appreciate the continuous help of Professor V. P. Gudkov for the interpretation of the measured results. The neutron experiments at the Materials and Life Science Experimental Facility of J-PARC were performed under the user program (Proposals No. 2011B0042, No. 2012A0122, No. 2012B0236, No. 2013B0189, No. 2014A0285, No. 2014B0348, No. 2015A0245, No. 2016B0200, No. 2016B0202, No. 2017A0158, No. 2017A0170, and No. 2017A0203). This work was supported by the Neutron Science Division of KEK as S-type research projects with program numbers 2014S03 and 2015S12. This work was partially supported by MEXT KAKENHI Grant No. JP19GS0210 and JSPS KAKENHI Grant No. JP17H02889.
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/3/27
Y1 - 2018/3/27
N2 - The angular distribution of individual γ rays, emitted from a neutron-induced compound-nuclear state via radiative capture reaction of La139(n,γ) has been studied as a function of incident neutron energy in the epithermal region by using germanium detectors. An asymmetry ALH was defined as (NL-NH)/(NL+NH), where NL and NH are integrals of low- and high-energy region of a neutron resonance respectively, and we found that ALH has the angular dependence of (Acosθγ+B), where θγ is the emitted angle of γ rays, with A=-0.3881±0.0236 and B=-0.0747±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 use the result to quantify the possible enhancement of the breaking of time-reversal invariance in the vicinity of the p-wave resonance.
AB - The angular distribution of individual γ rays, emitted from a neutron-induced compound-nuclear state via radiative capture reaction of La139(n,γ) has been studied as a function of incident neutron energy in the epithermal region by using germanium detectors. An asymmetry ALH was defined as (NL-NH)/(NL+NH), where NL and NH are integrals of low- and high-energy region of a neutron resonance respectively, and we found that ALH has the angular dependence of (Acosθγ+B), where θγ is the emitted angle of γ rays, with A=-0.3881±0.0236 and B=-0.0747±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 use the result to quantify the possible enhancement of the breaking of time-reversal invariance in the vicinity of the p-wave resonance.
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U2 - 10.1103/PhysRevC.97.034622
DO - 10.1103/PhysRevC.97.034622
M3 - Article
AN - SCOPUS:85045011471
VL - 97
JO - Physical Review C
JF - Physical Review C
SN - 2469-9985
IS - 3
M1 - 034622
ER -