Electric Dipole Moments, New Forces and Dark Matter

https://arxiv.org/abs/2008.09116

In this paper with Pavel Fileviez Perez, we study electric dipole moments in gauge theories where a dark matter candidate is predicted by the cancellation of gauge anomalies.

In theories Beyond the Standard Model where baryon and/or lepton number are promoted to local gauge symmetries, we need to introduce new fields to cancel all gauge anomalies. One of these fermions is neutral and automatically stable which makes it a good dark matter candidate. In addition, these models can naturally accommodate new sources of CP violation.

The new anomaly-cancelling fermions lead to electric dipole moments (EDMs) of the electron and the neutron via two-loop Barr-Zee diagrams. Namely, the charged fermions run in the loop in this diagram:

A crucial point is that not overproducing dark matter gives an upper bound on the symmetry breaking scale of the new U(1) group. Since the new charged fermions get their mass from this scale, this represents an upper bound on their masses.

We computed the EDMs and showed that, for large values of the CP-violating phase, future experiments that search for the EDM of the electron such as ACME will fully probe these theories.

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