Electron electric dipole moment
- Electron electric dipole moment
The electron electric dipole moment (EDM) is, roughly speaking, a measure of the charge distribution within an electron. Within the standard model of elementary particle physics, such a dipole is predicted to be of smaller than [Citation |last=Hoogeveen |first=F. |journal=Nucl. Phys. B |volume=341 |pages=322 |year=1990 |doi=10.1016/0550-3213(90)90182-D |title=The standard model prediction for the electric dipole moment of the electron] , where e stands for the elementary charge. The existence of a nonzero electron electric dipole moment would imply a violation of both parity invariance and time reversal invariance. [Citation |last1=Khriplovich |first1=I. B. |last2=Lamoreaux |first2=S. K. |title=CP Violation Without Strangeness: Electric Dipole Moments of Particles, Atoms, and Molecules |place=Berlin |publisher=Springer-Verlag |year=1997]
The Particle Data Group publishes its value as (.07±.07)×10−26"e" cm. The most recent experiment performed at the University of California at Berkeley placed an upper bound on (with a 90% confidence level) of . [Citation |last1=Regan |first1=B. |last2=Commins |first2=E. |last3=Schmidt |first3=S. |last4=Demille |first4=D. |journal=Phys. Rev. Lett. |volume=88 |pages=071805 |year=2002 |doi=10.1103/PhysRevLett.88.071805 |url=http://prola.aps.org/abstract/PRL/v88/i7/e071805 |title=New Limit on the Electron Electric Dipole Moment]
Many extensions to the standard model have been proposed in the past two decades. These extensions generally predict larger values for the electron EDM. For instance, the various technicolor models predict that ranges from . Supersymmetric models predict that . [Citation |last1=Arnowitt |first1=R. |last2=Dutta |first2=B. |last3=Santoso |first3=Y. |journal=Phys. Rev. D |volume=64 |pages=113010 |year=2001 |title=Supersymmetric phases, the electron electric dipole moment and the muon magnetic moment |url=http://prola.aps.org/abstract/PRD/v64/i11/e113010 |doi=10.1103/PhysRevD.64.113010] .
The present experimental limit is therefore close to eliminating some of these theories. Further improvements, or a positive result, would place further limits on which theory takes precedence.
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