# 2019 Symposium on Nuclear Data 2019年度核データ研究会

28-30 November 2019
C-CUBE, Kyushu University Chikushi Campus 九州大学筑紫キャンパス総合研究棟 (C-Cube)
Asia/Tokyo timezone
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# Study of an angular correlation of $\gamma$-rays emitted by 117Sn(n,$\gamma$) reactions for T-violation search

• Mr. Jun KOGA

## Abstract

The breaking of parity symmetry and charge conjugation (CP-violation) is necessary to explain a difference between the number of matter and that of antimatter in the current universe. Assuming the CPT theorem, CP-violation means the violation of time reversal invariance. It is theoretically suggested that T-violation could be enhanced in compound nuclear reactions by an interference between an amplitude of a s-wave resonance and that of a p-wave resonance. This theory predicts that one of key parameters for T-violation search is a spin factor $\kappa$(J) which corresponds to experimental sensitivity. The value of $\kappa$(J) depends on nuclear species and can be determined by measuring an angular correlation of $\gamma$-rays produced by (n,$\gamma$) reactions which compound nuclear state in a p-wave resonance decays to a specific state. If a nucleus has large $\kappa$(J), it becomes a candidate for T-violation search. To determine the value of $\kappa$(J) of 117Sn, which is easy to measure angular correlation because its p-wave resonance ca be clearly observed, we measured the angular correlation of $\gamma$-rays emitted from the compound states at J-PARC MLF BL04. The angular correlation was observed clearly when the compound state decays to a ground state. In addition, we conducted an experiment for determining a branching ratio which the compound state decays to the ground state in the (n,$\gamma$) reaction. In this poster, we will report the experimental result and analysis status.