Measurements of circular polarization from the 0.75-eV p-wave resonance of the La(n,)La reaction

Endo, Shunsuke   ; Fujioka, Hiroyuki*; Goto, Yu*; Ino, Takashi*; Iwamoto, Osamu  ; Iwamoto, Nobuyuki  ; Kawamura, Shiori*; Kimura, Atsushi   ; Kitaguchi, Masaaki*; Kobayashi, Ryuju; Nakamura, Shoji  ; Oku, Takayuki   ; Okudaira, Takuya*; Okuizumi, Mao*; Rovira Leveroni, G.  ; Shima, Tatsushi*; Shimizu, Hirohiko*; Takada, Shusuke*; Takahashi, Shingo*; Yoshikawa, Hiromoto*; Yoshioka, Tamaki*

The NOPTREX collaboration aims to search for time-reversal symmetry breaking (T-violation) using compound nuclear reactions. To elucidate the mechanism of T-violation in compound nuclear reactions, we are measuring the spin-angle correlation term of the (n,) reaction. We have already successfully measured the angular distribution and transverse asymmetry of emitted gamma-rays for several nuclei, such as La and Sn. As the next step, we measured the circular polarization of the emitted gamma-rays from the 0.75-eV p-wave resonance of La(n,)La reactions. The measurements were performed at J-PARC MLF BL04 (ANNRI). The circular polarization of gamma-rays was measured using the developed gamma-ray polarimeter. Although the circular polarization observed was weak, this first measurement on the resonances allowed us to place limits on the circular polarization from the p-wave resonance. In this presentation, we will report the details of the experiment and future plans.