Searches for P-Wave Resonances and Parity Violation in 140

Sensitive searches for new sources of time reversal violation in and among nucleons are one of the highest scientific priorities in nuclear/particle/astrophysics. The NOPTREX collaboration proposes a sensitive search for a time-reversal odd (T) and parity-odd (P) term in the neutron-nucleus forward scattering amplitude on the 0.734 eV p-wave resonance in ¹³⁹La. To see whether or not there might be additional strong candidates for the NOPTREX search, we conducted (n, $\gamma$) spectroscopy measurements and parity violation searches in 1403He neutron spin filter based on spin-exchange optical pumping [3], a ⁶Li neutron transmission detector, and a new NaI gamma detector array . We will present our findings from measurements conducted at both LANSCE and JPARC.

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[2] J. D. Bowman and V. P. Gudkov, Phys. Rev. C 90, 065503 (2014).

[3] D.C. Schaper, et al, Nuclear Instruments and Methods in Physics Research Section A, 969 (2020).