Standard Model Prediction for Paramagnetic Electric Dipole Moments
Yohei Ema, Ting Gao, Maxim Pospelov
Abstract
Standard model CP violation associated with the phase of the Cabibbo-Kobayashi-Maskawa quark mixing matrix is known to give small answers for the electric dipole moment (EDM) observables. Moreover, predictions for the EDMs of neutrons and diamagnetic atoms suffer from considerable uncertainties. We point out that the CP-violating observables associated with the electron spin (paramagnetic EDMs) are dominated by the combination of the electroweak penguin diagrams and ΔI=1/2 weak transitions in the baryon sector, and are calculable within chiral perturbation theory. The predicted size of the semileptonic operator C_{S} is 7×10^{-16}, which corresponds to the equivalent electron EDM d_{e}^{eq}=1.0×10^{-35} e cm. While still far from the current observational limits, this result is 3 orders of magnitude larger than previously believed.