Order of Magnitude Smaller Limit on the Electric Dipole Moment of the Electron

By A. J. Baron, W. C. Campbell, D. DeMille, J. Doyle, G. Gabrielse, Y. Gurevich, P. Hess, N. Hutzler, E. Kirilov, I. Kozyryev and 7 more. Science, 2013

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Stubbornly Spherical The shape of the electron's charge distribution reflects the degree to which switching the direction of time impacts the basic ingredients of the universe. The Standard Model (SM) of particle physics predicts a very slight asphericity of the charge distribution, whereas SM extensions such as supersymmetry posit bigger and potentially measurable, but still tiny, deviations from a perfect sphere. Polar molecules have been identified as ideal settings for measuring this asymmetry, which should be reflected in a finite electric dipole moment (EDM) because of the extremely large effective electric fields that act on an electron inside such molecules. Using electron spin precession in the molecule ThO, Baron et al. (p. 269, published online 19 December; see the cover; see the Perspective by Brown) measured the EDM of the electron as consistent with zero. This excludes some of the extensions to the SM and sets a bound to the search for a nonzero EDM in other facilities, such as the Large Hadron Collider. Spin precession measurements in the polar molecule thorium monoxide indicate a nearly spherical charge distribution of an electron. [Also see Perspective by Brown] The Standard Model of particle physics is known to be incomplete. Extensions to the Standard Model, such as weak-scale supersymmetry, posit the existence of new particles and interactions that are asymmetric under time reversal (T) and nearly always predict a small yet potentially measurable electron electric dipole moment (EDM), de, in the range of 10−27 to 10−30 e·cm. The EDM is an asymmetric charge distribution along the electron spin (S→) that is also asymmetric under T. Using the polar molecule thorium monoxide, we measured de = (–2.1 ± 3.7stat ± 2.5syst) × 10−29 e·cm. This corresponds to an upper limit of | de | < 8.7 × 10−29 e·cm with 90% confidence, an order of magnitude improvement in sensitivity relative to the previous best limit. Our result constrains T-violating physics at the TeV energy scale.

Subfields: Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2617a80a46f0e2748ad36a9e82dcc25b405fd63f

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Citations in the corpus

Electroweak phase transition and baryogenesis in composite Higgs models (2018, background): “d by electric and chromoelectric dipole moments (EDMs)7. The strongest bounds result from the former [67], which aect the electron EDM which is currently bounded to be d e=e<8:7 10 29 cm @ 90% CL [68] (see also [69{71]). This gives the constraint [67] Im[ qq~h] . 0:018 @90%CL: (7.11) Future exper”
Roadmap on STIRAP applications (2019, methodology): “The first-generation ACME I experiment used an optical pumping scheme to prepare the dark state required for the spin precession measurement with only 6% efficiency [28].”
Stimulated Raman adiabatic passage in physics, chemistry, and beyond (2016, methodology): “Further modifications in the experiment are expected to lead to an improvement of the sensitivity by an order of magnitude over the most recent results (Baron et al., 2014) with STIRAP making the largest single contribution (Gabrielse, 2016).”
Measuring the electric dipole moment of the electron in BaF (2018, methodology): “ered particles and the eEDM value in dierent types of models is illustrated in Fig. 1. The blue and green lines show the limits on the eEDM set by experiments with molecular beams of YbF [7] and ThO [8], respectively. The purple line shows the limit aimed at in our experiment with BaF. It is obvious”
Electric dipole moments in two-Higgs-doublet models (2013, methodology): “The presently most constraining measurement from this class is performed with ThO [51].”
Accidental composite dark matter (2015, neutral): “L [52].”
Antinuclei in heavy-ion collisions (2018, background): “To date, no candidate electric dipole moment signal has been observed, and recent atomic physics measurements have achieved about a ten-fold improvement in the upper limit on the electron’s electric dipole moment that significantly constrains T -violating physics [86].”
Electric dipole moments of atoms, molecules, nuclei, and particles (2017, methodology): “In Figure 31, we plot de vs CS for the d exp para for ThO and HfF+ along with 68% and 95% confidence-level contours for χ2 on the de-CS space, where χ2 = ∑ i [ dexpi − de − (αCS αde ) i CS ]2 σ2i .”
Renormalization group evolution of the Standard Model dimension six operators III: gauge coupling dependence and phenomenology (2013, methodology): “69) using the recently measured upper bound [95], de < 1.”
Physics of leptoquarks in precision experiments and at particle colliders (2016, background): “The strongest constraint has been obtained for the EDM of neutron [236], the (199)Hg atom [237] and the ThO molecule [238].”