Permanent electric dipole moments of particles and atoms

4 problems

• Is the electron EDM nonzero above 1e-31 e cm?

  Open

  No electron dipole has been seen down to 4 parts in $10^{30}$ of an electron charge times a centimeter. Next-generation molecule experiments aim to look ten times deeper, where many theories with new heavy particles predict a signal.

• Is the neutron EDM nonzero at the 1e-27 e cm level?

  Open

  Slow neutrons stored in a bottle precess in electric and magnetic fields, and a dipole would shift their precession rate when the electric field is flipped. No shift has yet been seen.

• Controlled nuclear-theory values for Schiff moments of Hg-199 and Ra-225

  Open

  Atoms like mercury and radium are sensitive to time-reversal violation inside the nucleus, through a quantity called the Schiff moment (the part of the nuclear charge distribution that the electrons cannot screen). Turning atomic measurements into statements about quarks and gluons needs the Schiff moment computed reliably, and present calculations disagree by large factors.

• Which set of EDM measurements fixes all low-energy CP-odd parameters?

  Open

  Many different microscopic causes could produce dipoles in electrons, neutrons and atoms, and one measurement cannot tell them apart. The question is which combination of experiments would pin down each cause separately.