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SUMMARY:Improved measurement of the electron EDM - Prof. Edward Hinds (Imp
 erial College London)
DTSTART:20111018T140000Z
DTEND:20111018T150000Z
UID:TALK32600@talks.cam.ac.uk
CONTACT:John Marshall
DESCRIPTION:The electron’s charge distribution can be characterised by i
 ts electric dipole moment (EDM)\, de\, which measures the deviation of its
  electric interactions from purely spherical. According to the standard mo
 del\, this EDM is de≈10-38e.cm – some eleven orders of magnitude below
  the current experimental limit. However\, most extensions to the standard
  model predict much larger values\, potentially accessible to measurement(
 1). Hence\, the search for the electron EDM is a search for physics beyond
  the standard model. Moreover\, a non-zero de breaks time-reversal symmetr
 y which\, in many models of particle physics\, is equivalent to breaking t
 he symmetry between matter and antimatter\, known as CP symmetry.  New CP-
 breaking physics is thought to be needed to explain the existence of a mat
 erial universe(2). We have used a supersonic beam of cold YbF molecules to
  measure the electron EDM\, obtaining the result de=-2.4±5.7stat±1.5syst
 ×10-28e.cm and setting a new upper limit of de < 10.5×10-28e.cm with 90%
  confidence(3). Our result\, consistent with zero\, indicates that the ele
 ctron is spherical at this improved level of precision. Our measurement\, 
 of atto-eV energy shifts in a molecule\, probes new physics at the tera-eV
  energy scale. Many extensions to the standard model\, such as the minimal
  supersymmetric standard model\, naturally predict large EDMs and our meas
 urement places significant constraints on the parameters of these theories
 (4).\n\n(1) E. D. Commins\, Electric dipole moments of leptons\, in Advanc
 es in Atomic\, Molecular\, and Optical Physics\, Vol. 40\, B. Bederson and
  H.Walther (Eds.)\, Academic Press\, New York\, pp. 1-56 (1999).\n\n(2) A.
  D. Sakharov\, Violation of CP invariance\, C asymmetry\, and baryon asymm
 etry of the universe\, Pis’ma ZhETF 5\, 32 (1967). [Sov. Phys. JETP Lett
 . 5\, 24 (1967).]\n\n(3) J. J. Hudson\, D. M. Kara\, I. J. Smallman\, B. E
 . Sauer\, M. R. Tarbutt\, E. A. Hinds “Improved measurement of the shape
  of the electron”\, Nature 473\, 493 (2011). doi:10.1038/nature10104\n\n
 (4) E. D. Commins and D. DeMille\, “The electric dipole moment of the el
 ectron”\, Chapter 14 in Lepton Dipole Moments Eds. B. L. Roberts and W. 
 J. Marciano\, (World Scientific\, Singapore 2010).
LOCATION:Rutherford Seminar Room B
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