Abstract
An improved measurement of the electron electric dipole moment (EDM) appears feasible using ground-state alkali atoms in an atomic fountain in which a strong electric field, which couples to a conceivable electron dipole moment (EDM), is applied perpendicular to the fountain axis. In a practical fountain, the ratio of the atomic tensor Stark shift to the Zeeman shift is a facto mu~100. We expand the complete time evolution operator in inverse powers of this ratio; complete results are presented for atoms of total spin F=3, 4, and 5. For a specific set of entangled hyperfine sublevels (coherent states), potential systematic errors enter only as even powers of 1/mu, making the expansion rapidly convergent. The remaining EDM mimicking effects are further suppressed in a proposed double-differential setup, where the final state is interrogated in a differential laser configuration, and the direction of the strong electric field also is inverted. Estimates of the signal available at existing accelerator facilities indicate that the proposed apparatus offers the potential for a drastic improvement in EDM limits over existing measurements, and for constraining the parameter space of supersymmetric (SUSY) extensions of the Standard Model.
Highlights
We present a complete categorization of all systematic errors that result from an atom in an atomic fountain being subjected to a constant electric field, the motional magnetic field, and trace magnetic fields which are static but may vary arbitrarily in all three spatial directions
We set up the formalism for the theoretical description of the quantum dynamics of an alkali atom within an atomic fountain designed for an electric dipole moment (EDM) experiment
The low velocity of the atoms inside a fountain reduces the motional magnetic field, which arises as the Lorentz transformation of the applied electric field, by a factor of 100 compared to experiments on thermal atomic beams
Summary
A permanent electric dipole moment of the electron or of any other fundamental particle, or of an atom in an eigenstate of angular momentum, is possible only if the symmetries of both parity (P ) and time-reversal (T ) are violated [1,2]. Extensions of the Standard Model generically contain new massive particles and new sources of CP violation that give rise to an electric dipole moment (EDM) for the electron. In the absence of a special structure that would otherwise constrain the form factor F3 to be small, field theories that extend the Standard Model generally contain a significant EDM. Present limits on the electron EDM [14,15] are lower by a factor of 100 than EDMs predicted by some SUSY models [16–21] with superpartner masses of 100 GeV and CP -violating phases of order unity. If more accurate experimental results still turn out to be compatible with a zero EDM, one will begin to exhaust some of the simpler remedies and push the theory toward constructions inconsistent with the original motivations for SUSY
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