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Abstract The current best upper limit for electron electric dipole moment (EDM), |d e |<1.1×10 -29 e·cm (90% confidence), was set by the ACME collaboration in 2018. The ACME experiment uses a spin-precession measurement in a cold beam of ThO molecules to detect d e . An improvement in statistical uncertainty would be possible with more efficient use of molecules from the cryogenic buffer gas beam source. Here, we demonstrate electrostatic focusing of the ThO beam with a hexapole lens. This results in a factor of 16 enhancement in the molecular flux detectable downstream, in a beamline similar to that built for the next generation of ACME. We also demonstrate an upgraded rotational cooling scheme that increases the ground state population by 3.5 times compared to no cooling, consistent with expectations and a factor of 1.4 larger than previously in ACME. When combined with other demonstrated improvements, we project over an order of magnitude improvement in statistical sensitivity for the next generation ACME electron EDM search.
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Measurement of the H3∆₁ Radiative Lifetime in ThO
The best limit on the electron electric dipole moment (eEDM) comes from the ACME II experiment [Nature \textbf{562} (2018), 355-360] which probes physics beyond the Standard Model at energy scales well above 1 TeV. ACME II measured the eEDM by monitoring electron spin precession in a cold beam of the metastable H3Δ1 state of thorium monoxide (ThO) molecules, with an observation time τ≈1 ms for each molecule. We report here a new measurement of the lifetime of the ThO (H3Δ1) state, τH=4.2±0.5 ms. Using an apparatus within which τ≈τH will enable a substantial reduction in uncertainty of an eEDM measurement.
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- Award ID(s):
- 2136573
- PAR ID:
- 10342313
- Date Published:
- Journal Name:
- ArXivorg
- ISSN:
- 2331-8422
- Page Range / eLocation ID:
- 2204.05904
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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