Searching for time-reversal symmetry violation with molecular ions: Quantum state control and photofragment imaging

The relative abundance of matter over antimatter in the observable universe cannot be ac-counted for by the Standard Model of particle physics (SM), and requires additional sources of time-reversal symmetry violation to be explained. Theories seeking to explain this imbalance generically predict electric dipole moments of fundamental particles such as the electron. We search for the electron’s electric dipole moment (eEDM) using HfF+ molecular ions confined in a radiofrequency trap, polarized by a rotating electric bias field. We have produced a first result with this system that is consistent with zero, setting an upper bound |de| < 1.3 × 10−28 e cm (90% confidence) –equivalent to setting a lower bound on the mass of beyond SM particles of several TeV. In this thesis, we describe the first generation measurement and progress towards a second-generation measurement with more than an order of magnitude improved sensitivity. In particular, we discuss quantum state preparation of molecular ions by optical pumping, and a new technique for simulta-neous differential measurement of molecules with opposite orientations, which allows us to attain the shot-noise limit with hundreds of detected ions and multi-second coherence.
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Department of Physics
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University of Colorado Boulder
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