Searching for hadronic CP violation using ultracold assembled FrAg molecules

We present a new approach to search for flavor-conserving hadronic CP violation (FCH-CPV) by measuring the $^{223}$Fr nuclear Schiff moment. The $^{223}$Fr nucleus (t$_{1/2}}$ = 22 minutes) is believed to have a static octupole deformation that leads to a $sim$300-fold enhancement in the size of its Schiff moment, for a given strength of FCH-CPV interactions [1]. By binding Fr with Ag atoms, we will form a strongly polar molecule that further amplifies the observable CP-violating energy shift [2,3]. By using modern atomic physics techniques such as laser cooling, quantum-coherent molecular binding via Feshbach resonances and stimulated Raman adiabatic passage, and optical trapping, trapped ensembles of FrAg molecules can be formed in a single quantum state [4, 5]. Assuming molecule numbers and spin coherence times already demonstrated in analogous molecular systems, we project a factor of ~1000 improvement in sensitivity to underlying FCH-CPV physics. A necessary step towards this goal is gaining full quantum control over Ag and Fr atomic gases. Here we present steps towards this including magneto-optical trapping of Ag, sub-Doppler cooling, and progress towards measuring ultracold Ag-Ag scattering properties. We also describe developments towards offline sources of $^{221}$Fr and $^{223}$Fr based on decay of long-lived parent isotopes.

[1] Spevak et al., Phys. Rev. C 56, 1357 (1997).

[2] Fleig & DeMille, New J. Phys. 23, 113039 (2021).

[3] Śmiałkowski & Tomza, Phys. Rev. A 103, 022802 (2021).

[4] Kłos et al., New J. Phys. 24, 025005 (2022).

[5] Molony et al., Phys. Rev. Lett. 113, 255301 (2014).