Nuclear spin-dependent parity nonconservation in molecules

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This experimental research program will shed light on the nature of parity nonconserving (PNC) interactions inside the nucleus, via the study of nuclear anapole moments. A deviation of the measured results from theoretical expectations could serve as evidence for new phenomena at an energy scale beyond that directly accessible to any planned accelerator; or could change our understanding of how electroweak physics is modified in the presence of nuclear matter. The proposed technique is related to previous studies of atomic PNC, but uses diatomic molecules rather than atoms to achieve a dramatic increase in sensitivity. The small energy splittings and the narrow spectral lines associated with hyperfine/rotational structure in molecules enhance the size of weak interaction effects by several orders of magnitude. This will make it possible for the first time to observe nuclear spin-dependent PNC effects from many different nuclei, over a wide range of mass numbers A, carrying both valence protons and valence neutrons. The ability to combine many observations will make it possible to completely characterize the different contributions to nuclear spin-dependent PNC effects. The broader impact of the program will involve extensive student training as well as several collaborations. This award is funded jointly through the Atomic, Molecular, Optical and Plasma Physics Program and the Nuclear Physics Program in the Physics Division.