Abstract
We recently set a new limit on the electric dipole moment of the electron (eEDM) (J Baron et al and ACME collaboration 2014 Science 343 269–272), which represented an order-of-magnitude improvement on the previous limit and placed more stringent constraints on many charge-parity-violating extensions to the standard model. In this paper we discuss the measurement in detail. The experimental method and associated apparatus are described, together with the techniques used to isolate the eEDM signal. In particular, we detail the way experimental switches were used to suppress effects that can mimic the signal of interest. The methods used to search for systematic errors, and models explaining observed systematic errors, are also described. We briefly discuss possible improvements to the experiment.
Highlights
Symmetries play a vital role in physics and experimental tests of symmetries have revealed insights into physical theory
While any such estimates are inherently model-dependent, we see that using an apparatus that fits in a room we have been able to probe fundamental physics at energy scales usually associated with the largest particle accelerators
We examined the correlations of these quantities with the experiment switches to determine whether there are any spurious signals that might point to unforeseen systematic errors, or a gap in our understanding of the experiment [65]
Summary
Symmetries play a vital role in physics and experimental tests of symmetries have revealed insights into physical theory. The eEDM arises as a radiative correction (Feynman loop diagram) due to CP -violating interactions with new particles. An example of such an interaction within generic supersymmetric theory is shown in figure 1. For a given CP -violating phase φCP , one can make a generic estimate of the mass scale Λ of new physics being probed, according to the following formula for an n-loop process [24]: Λ2. Similar analysis shows that our result was sensitive to twoloop effects at around the 1 TeV mass scale While any such estimates are inherently model-dependent, we see that using an apparatus that fits in a room we have been able to probe fundamental physics at energy scales usually associated with the largest particle accelerators
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