The metastable Q 3Δ2^3\Delta_2 state of ThO: A new resource for the ACME electron EDM search

The best upper limit for the electron electric dipole moment was recently set by the ACME collaboration. This experiment measures an electron spin-precession in a cold beam of ThO molecules in their metastable $H~(^3\Delta_1)$ state. Improvement in the statistical and systematic uncertainties is possible with more efficient use of molecules from the source and better magnetometry in the experiment, respectively. Here, we report measurements of several relevant properties of the long-lived $Q~(^3\Delta_2)$ state of ThO, and show that this state is a very useful resource for both these purposes. The $Q$ state lifetime is long enough that its decay during the time of flight in the ACME beam experiment is negligible. The large electric dipole moment measured for the $Q$ state, giving rise to a large linear Stark shift, is ideal for an electrostatic lens that increases the fraction of molecules detected downstream. The measured magnetic moment of the $Q$ state is also large enough to be used as a sensitive co-magnetometer in ACME. Finally, we show that the $Q$ state has a large transition dipole moment to the $C~(^1\Pi_1)$ state, which allows for efficient population transfer between the ground state $X~(^1\Sigma^+)$ and the $Q$ state via $X-C-Q$ Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate $90\,$% STIRAP transfer efficiency. In the course of these measurements, we also determine the magnetic moment of $C$ state, the $X\rightarrow C$ transition dipole moment, and branching ratios of decays from the $C$ state.Comment: 21 pages, 6 figures, 5 pages appendice

Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

Electric dipole moments and the search for new physics

Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well beyond those reached directly at high energy colliders. Discrimination between different physics models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss the current status and prospects in the near future for a compelling suite of such experiments, along with developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and endorsement

Neutrinos

229 pages229 pages229 pagesThe Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, and nucleons, nuclei, and atoms