A Precision Measurement of the Parity Violation Present in the 0.734 eV p-wave Resonance in $^{139}$La Using the \lq{Double Lanthanum}\rq \ Technique: Preliminary Results and Analysis*

The Neutron OPtics Time Reversal EXperiment (NOPTREX) Collaboration aims to measure a potential time-reversal (T) violating process in neutron-nucleon forward scattering in parity (P) violating  nuclear resonances. Because the proposed theoretical T-violating cross section is directly proportional to a P-violating cross section, precision spectroscopy of these resonances is of critical importance. In particular, the 0.734 eV p-wave resonance in $^{139}$La exhibits a ~10\% P-violation effect, making it an outstanding candidate for the NOPTREX experiment. We aim to measure this effect to 1\% precision, improving upon previous (room temperature) measurements by using cryogenic targets (15K) to reduce Doppler broadening effects as well as running for a longer period of time to reduce the statistical uncertainty. This experiment was conducted at LANSCE in 2017-2018. This talk will focus on the experimental setup, the preliminary data analysis and results, as well as future implications for the NOPTREX collaboration and additional parity-violation experiments on heavy nuclei.