Nuclear Spin-Dependent Parity Nonconservation in Diatomic Molecules

Nuclear spin-dependent parity nonconservation (NSD-PNC) effects arise from couplings of the $Z_0$ boson (parameterized by the electroweak coupling constants $C_{2P,N}$) and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The effects of the anapole moment scale with the nucleon number A of the nucleus as $A^{2/3}$, while the $Z_0$ coupling is independent of A; the former will be the dominant source of NSD-PNC in nuclei with A $>$ 20. To date, the most precise result on NSD-PNC comes from a measurement of the hyperfine dependence of atomic PNC in $^{133}Cs$. However, the effects of NSD-PNC can be dramatically enhanced in diatomic molecules. We outline an experimental program to take advantage of this enhancement. We have identified over ten suitable molecules; from measurements on the nuclei in these molecules we can extract the relative contributions of the anapole moment and the electroweak $Z_0$ couplings. This will increase the available data on nuclear anapole moments, as well as reduce the uncertainties in current measurements of $C_{2N}$ and $C_{2P}$. We report on the design of our pulsed molecular beam experiment and the current status of our efforts.