A First Measurement of the Spin-Dependent Neutron-Nucleus Forward Scattering Amplitudes in Polarized Neutron-Polarized $^{131}$Xe and $^{129}$Xe Nuclei Using Pseudomagnetic Precession

Spin-dependent amplitudes in polarized neutron-polarized nucleus forward scattering can cause systematic errors in NOPTREX. We performed the first measurement of neutron pseudomagnetic precession\footnote{Zimmer, O., Ehlers, G., Farago, B. et al. A precise measurement of the spin-dependent neutron scattering length of 3He. EPJ direct 4, 1–28 (2002). https://doi.org/10.1007/s1010502a0001} in neutron transmission through polarized $^{131}$Xe and $^{129}$Xe with the J-NSE Neutron Spin Echo spectrometer at FRM II reactor facility in Germany\footnote{Heinz Maier-Leibnitz Zentrum. (2015). J-NSE: Neutron spin echo(NSE) spectrometer. Journal of large-scale research facilities, 1, A11. http://dx.doi.org/10.17815/jlsrf-1-34}. The Xenon nuclei were polarized using an in-situ Spin Exchange Optical Pumping system. We extracted pseudomagnetic precession angles from phase-sensitive NSE signals and then calculated the corresponding incoherent scattering lengths. We will present the experimental setup of the polarized Xenon pseudomagnetic precession measurement, the data analysis procedure, the result and its implication.