26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Tabletop particle physics with BaOH: Molecular structure theory for next-gen precision measurements of time-reversal symmetry violation

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Atomic and Molecular Physics (ATMOP)

Description

Despite decades of indisputable success, the Standard Model (SM) of particle physics is known to be incomplete. Indeed, explaining the observed matter-antimatter asymmetry in the Universe, given equal generation of both during the Big Bang, remains one of the most pressing problems in theoretical physics. While the SM contains a source of charge-parity (CP) violation within the quark mixing Cabibbo-Kobayashi-Maskawa matrix, the magnitude of this contribution is insufficient to adequately account for the origin of this asymmetry. This provides strong motivation to search for additional sources of CP violation that may arise in SM extensions. A low energy “table-top” approach is to measure the permanent electric dipole moments of fundamental particles within atoms and molecules, the existence of which requires time-reversal (and hence CP) symmetry violation. The current upper bound for the free electron EDM (eEDM) obtained from the JILA HfF$^+$ experiment places constraints on supersymmetric, technicolour, left right symmetric and multi-Higgs theories at energy scales inaccessible with even the largest colliders presently in use. By offering several advantages in the suppression of systematic effects, polyatomic molecules provide a platform for next-generation precision measurements capable of probing new physics at the PeV scale.
A recent proposal by the NL-eEDM collaboration has identified barium monohydroxide (BaOH) as a promising candidate for future experiments. Given that barium containing molecules are expected to lie in the optical regime, the relative simplicity associated with cooling and trapping has the potential to compensate for any potential loss of sensitivity compared to molecules containing heavier elements.
Accurate electronic structure theory is essential for constructing effective Hamiltonians that describe the rotational, vibrational, fine and hyperfine structure of complex molecules. In this work, we present recent advances in the theoretical characterisation of BaOH and discuss the potential implications for the planning, execution, and interpretation of next-generation eEDM measurements.