EPJ Web of Conferences (Jan 2019)

Measurement of the angular distribution of γ-rays after neutron capture by 139La for a T-violation search

  • Okudaira Takuya,
  • Shimizu Hirohiko M.,
  • Kitaguchi Masaaki,
  • Hirota Katsuya,
  • Haddock Christopher C.,
  • Ito Ikuya,
  • Yamamoto Tomoki,
  • Endo Shunsuke,
  • Ishizaki Kohei,
  • Sato Takumi,
  • Takada Shusuke,
  • Koga Jun,
  • Yoshioka Tamaki,
  • Ino Takashi,
  • Asahi Kouichiro,
  • Momose Takamasa,
  • Iwata Takahiro,
  • Oku Takayuki,
  • Sakai Kenji,
  • Kimura Atsushi,
  • Nakao Taro,
  • Hino Masanori,
  • Shima Tatsushi,
  • Yamagata Yutaka

DOI
https://doi.org/10.1051/epjconf/201921909001
Journal volume & issue
Vol. 219
p. 09001

Abstract

Read online

Parity violating effects enhanced by up to 106 times compared to proton-proton scattering have been observed in several neutron capture induced compound nuclei. This enhancement is explained as an interference between an s-wave and a p-wave amplitude (s-p mixing). Theory predicts that this mechanism can also enhance T-violating effects. For estimation of this enhancement in a promising candidate nucleus, we measured the angular distribution of γ-rays in the (n,γ) reaction induced in a 139La target. Experiments were performed at J-PARC, using a germanium detector array at an intense neutron beam. Analysis of the observed angular dependence around the 0.74 eV p-wave resonance allowed us to determine the ratio of the partial p-wave neutron width to the total neutron width in the entrance channel of the compound nucleus. We also report our development of a 3He spin filter needed as an epithermal-neutron polarizer for the T-violation search.