[math-fun] electron electric dipole moment, if any, is small
http://arxiv.org/abs/1310.7534 says electron electric dipole moment is (-2.1 +- 3.7stat +- 2.5syst) * 10^(-31) * e * meter. Press descriptions claim standard model predicts exactly zero. Really? Certainly plain QED predicts zero, but the weak force being chiral, and known T and P violations in the standard model, might perhaps allow a small nonzero value for electron, proton, or neutron electric dipole moments. I saw no basis for the (bogus?) claim made or implied in press descriptions of this, that the standard model forces these to be exactly 0. Indeed, I've seen claims SM predicts roughly neutron: 10^(-34) e * meter electron: 10^(-43) e * meter proton: 10^(-33) e * meter They say extensions to the standard model such as "weak scale supersymmetry," predict 10^(-32) to 10^(-29) e * meter for the electron electric dipole moment. They hope to wring another factor of 10 out of refined future versions of their experiment, which would mostly rule this out. How does their experiment work? Should we believe it? I follow that ThO is a highly polar neutral molecule, containing internal electric fields they say of 84 GV/cm, so if its electrons had an electric dipole moment I presume that would yield detectable energy level shifts and possible new spectral excitations. Why the hell whatever they measured proves there are no such... that was not clearly explained. Anyhow, if an electron had dipole moment D in units of e*meter, then expect energy shift of order 8.4*10^12 * D * ElectronVolt, so their claim |D|<10^(-30) means they believe they can somehow can rule out energy shifts of the order 10^(-17) ElectronVolts. I pointed out to them in email that if so, they ought to be able to show, by using ordinary nitrogen N2, that the electron electric QUADrupole |moment| is below about 0.001 barns*e. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
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Warren D Smith