Neutron Electric Dipole Moment Experiment
BU, Cal-Berkeley, Caltech, Duke, Hahn-Meitner, Harvard, Illinois,
ILL, Leiden, LANL, Maryland, NIST, New Mexico, ORNL, Simon-Fraser

The possible existence of a non-zero electric dipole moment of the neutron is of great fundamental interest and directly impacts our understanding of the nature of electro-weak and strong interactions. The experimental search for this moment has the potential to reveal new sources of T and CP violation and to challenge calcuations that propose extensions to the Standard Model. In addition, the small value for the neutron EDM continues to raise the issue of why the strength of the CP-violating terms in the QCD Lagrangian are so small. This seems to suggest the existence of a new fundamental symmetry that blocks strong CP-violating processes.

Schematic of proposed apparatus

Slow neutrons from the Spallation Neutron Source (ORNL) enter the apparatus from the right. They are trapped in L⁴He cells located between the green and red high-voltage plates. The trapped neutrons precess in a weak magnetic field; this precession rate is measured both when the electric field is parallel and anti-parallel to the magnetic field. Any difference in precession rates is proportional to the neutron electric dipole moment.

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