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Nuclear spin dependent parity violation effects in diatomic molecules

March 16, 2017 - 3:30pm
Emine Altuntas

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.

PSC 2136