- Electron electric dipole moment
The electron
electric dipole moment (EDM) d_e is, roughly speaking, a measure of the charge distribution within anelectron . Within thestandard model of elementary particle physics, such adipole is predicted to be of smaller than 10^{-40} mathrm{ e cm} [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 theelementary charge . The existence of a nonzero electron electric dipole moment would imply a violation of bothparity invariance andtime 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 d_e| < 1.6 imes 10^{-27} mathrm{e cm}. [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 model s predict d_e| that ranges from 10^{-27} - 10^{-29}mathrm{e} mathrm{cm} .Supersymmetric models predict that d_e| lesssim 10^{-26} mathrm{e} mathrm{cm} . [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.
References
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