The Electron EDM Project at LBNL
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Project Background | Experiment | Other projects

Lawrence Berkeley National Laboratory (LBNL) is a Department of Energy (DOE) laboratory situated in the hills above the University of California at Berkeley Campus. LBNL performs non-classified research in the fields of basic sciences, energy usage, energy conservation, and particle accelerators, among others. LBNL is managed by the Regents of the University of California. The Electron EDM Project is one part of the varied and exciting research being performed by LBNL's Atomic, Molecular & Optical (AMO) physics community.

PI Previous participants
Harvey Gould (email) Timothy P. Dinneen (Post doc)
Xingcan Dai
Grad Student Xinghua Lu
Jason M. Amini Chris Norris
(aka Jason A. Maddi) Timothy Page
Daniel Schwan
Andrew Ulmer
Charles Munger, SLAC

Project background

In this experiment, we are searching for a permanent electric dipole moment (EDM) of the electron. Classically, an EDM corresponds to the distortion of a spherical charge distribution. The electron is a point charge, as far as physicists can tell, but it could still have an analog to the classical EDM just as it has the analogs to a classical spin and magentic dipole moment.

The discovery of the EDM, even if tiny, would have major reprocusions on the mathematical models of particle physics. There are many models, but the currently accepted theory is called the Standard Model of particle physics. The Standard Model predicts an electron EDM much smaller than the one we could measure in the near future. However, this model has some unsatisfactory features and theorists have generated alternatives with some of the desired properties. So far, experimental results have been consistent with the Standard Model, so there has been no evidence as to which, if any, of these alternate theories are valid. In general, these alternate theories predict a considerably larger electron EDM which is in range of the current experimental techniques.

Either the EDM will be discovered in the current range, which would be evidence for physics beyond what is described by the Standard Model, or the EDM will be found to be smaller than is comfortably predicted by the alternate theories, which forces the theorists back to their pens and paper.


A direct measurement of the electron EDM would be difficult because the necessary electric fields would deflect the electron. Instead, we use the cesium atom as a neutral system to probe the electron properties. We are looking for a Stark effect (energy shift due to an electric field) in the cesium ground states that is linear in the applied electric field.

Our EDM apparatus has several distinctive features from other electron EDM measurements: a cold atom fountain replaces an atomic beam; the magnetic fields are measured and nulled as a function of atomic position instead of simply nulling the average field; an electric field quantizes the atoms instead of a magnetic field; and the atoms are prepared in various superpositions of states to reduce linewidths and measure systematic errors.

The apparatus showing the optics table and the tower with its support frame.
An ant's eye view of the tower.

A few of this group's other projects

Precision measurement of the cesium ground state polarizability and consequent derivations of C6 and the D1 and D2 lifetimes.

Phys. Rev. Lett. 91, 153001 (2003)

Neutral atom optics with static and pulsed electric fields.


"Slowing and cooling molecules and neutral atoms by time-varying electric-field gradients," Phys. Rev. A 60, 3882 (1999).

Transverse focusing with a tripplet lens (with George Kalnins):
Phys. Rev. A (in publication, 2005).

Quantum control of magnetic sublevels using electric and magnetic fields.
Molecular optics with static and pulsed electric fields.

With: Hiroshi Nishimura, Glen Lambertson, George Kalnins.


"Feasibility of a synchrotron storage ring for neutral polar molecules," Rev. Sci. Instrum. 74, 3271 (2003)

"Improved alternating gradient transport and focusing of neutral molecules," Rev. Sci. Instrum. 73, 2557 (2002)

Measurement of the differential polarizability of the D2 transition and the 6P3/2 tensor polarizability in cesium.

Page owner: Page last updated 7/8/05.