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The Search for Nuclear Anapole Moments in Diatomic Molecules:

March 13, 2014 - 12:00pm
Sidney Cahn
Yale University

Nuclear spin-dependent parity nonconservation (NSD-PNC) effects arise from exchange of the Z0 boson (parameterized by the electroweak coupling constants C2{P,N } ) between electrons and the nucleus, and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with the nucleon number A of the nucleus as A3/2, while the Z0 coupling is independent of A; the former will be the dominant source of NSD-PNC in nuclei with A ≥ 20. NSD-PNC effects can be dramatically amplified in diatomic molecules by bringing two levels of opposite parity close to degeneracy in a strong magnetic field. This opens the prospect for measurements across a broad range of nuclei. As a precursor to the measurement of the nuclear anapole moment of 137Ba, we have experimentally observed and characterized opposite-parity level crossings in 138BaF. These are found to be in excellent agreement with parameter-free predictions and indicate that the sensitivity necessary for NSD-PNC measurements should be within reach.  They have also provided a two-level system in which a form of molecular interferometer obtains, whose fringes exhibit Airy function-like behavior.  

Host: Luis A. Orozco

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