Spin dependence in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>-wave resonance of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">La</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>139</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow><mml:mo></mml:mo></mml:mover><mml:mo>+</mml:mo><mml:mover accent="true"><mml:mi>n</mml:mi><mml:mo></mml:mo></mml:mover></mml:mrow></mml:math>
Takuya Okudaira, R. Nakabe, C. J. Auton, Shunsuke Endo, Hiroyuki Fujioka, Vladimir Gudkov, Ichiro Ide, Takashi Ino, M. Ishikado, Wataru Kambara, Seiji Kawamura, Ryosaku Kobayashi, Masaaki Kitaguchi, T. Okamura, Takayuki Oku, J. G. Otero Munoz, Joseph D. Parker, K. Sakai, Tatsushi Shima, Hirohiko M. Shimizu, T. Shinohara, W. M. Snow, S. Takada, Y. Tsuchikawa, Ryutaro Takahashi, S. Takahashi, H. Yoshikawa, T. Yoshioka
Abstract
We measured the spin-dependent cross section at a neutron-induced $p$-wave resonance using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75 eV $p$-wave resonance of $^{139}\mathrm{La}+n$, where previous experiments have shown a large enhancement of parity violation. The spin dependence of the neutron absorption cross section of polarized $^{139}\mathrm{La}$ and polarized neutrons determines the partial neutron width of the $p$-wave resonance. This partial width is a key parameter needed to determine the sensitivity of this system to possible parity-odd and time reversal-odd interactions beyond the standard model. Our findings therefore serve as a foundation for a future search for time reversal violation in this compound nuclear system.