Nuclear spin dependent parity violation effects in diatomic molecules
Parity, one of the three discrete spacetime symmetries of nature is broken by weak interactions. In atomic systems, parity violation is manifested in two ways: nuclear spin independent and spin dependent effects. The former is a relatively large effect that has been measured to better than 1%, whereas the nuclear spin dependent parity violation (NSD-PV) effect is small and remains poorly understood. To date the only nonzero measurement of NSD-PV effects in atoms was made in Cs, but the uncertainty in this measurement is substantial (~15%) and the result is in disagreement with other data from nuclear physics. We study NSD-PV effects using diatomic molecules. NSD-PV effects mix levels of opposite parity, with the mixing inversely proportional to energy splitting between these levels. Molecules have opposite-parity rotational/hyperfine levels with energy splittings about four orders of magnitude smaller than the typical 1 eV atomic energy scale. We amplify observable signals from NSD-PV by about seven additional orders of magnitude by bringing two rotational levels of opposite parity close to degeneracy with a strong magnetic field. The resultant NSD-PV interaction is measured using a Stark-interference technique. I will present our latest results that demonstrate statistical sensitivity to NSD-PV effects surpassing that of any previous atomic PV measurement, using the test system 138BaF. I will also discuss our methods for measuring and nullifying systematic effects.
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