Thursday, May 26, 2011

Electron Dipole Moment Small

[W]e use cold polar molecules to measure the electron EDM at the highest level of precision reported so far, providing a constraint on any possible new interactions. We obtain de = (−2.4±5.7stat±1.5syst)×10−28ecm, where e is the charge on the electron, which sets a new upper limit of |de|<10.5×10−28ecm with 90 per cent confidence. This result, consistent with zero, indicates that the electron is spherical at this improved level of precision.

From Nature.

The Standard Model predicts a small electron dipole moment, as a consequence of the small charge parity violating phase in the CKM matrix, but that is far too small to be revealed in this experiment and most beyond the Standard Model theories predict a larger than Standard Model electron dipole moment.  Another factor of a hundred in precision, if it also reveals a result consistent with zero, would rule out many "beyond the standard model" theories of physics.  As it is, the new result, which is 1.5 times smaller than the previous standard set in 2002, merely tightens the constraints on theorists a bit more  than past results and confirm the general finding of past research that the electron dipole moment is very small.

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