Test of T-odd, P-even (TOPE) Symmetry Violation in Atoms

 

*** 1999 NIST Precision Measurement Grant awarded tofund this project ***

pdf version of 1999 NIST grant proposal (150 kB)

 

Unlike the situation for PNC (P-odd, T-even) or EDM (P-odd,T-odd) forces, for which there is a rich history of atomic experiments, very little is known about the nature of possible "TOPE" forces. Using our thallium atomic beam, we are proposing to undertake a sensitive search for such interactions. The basic idea is to search for a term in the atomic Hamiltonian describing the interaction of the thallium atoms with a static and laser field which would have the form: (k*E) where "k" represents the propagation direction of the laser, and "E" a static electric field. Such an interaction would be manifestly T-odd and P-even.

 

We would send counterpropagating laser beams (tuned to the same 1283 nm P_1/2 - P_3/2 transition already studied in the lab) around a high-finesse ring cavity which includes transverse interaction with the thallium atomic beam. The static electric field can be directed parallel to either laser beam (see schematic here). As with the ordinary electromagnetic interaction, the laser-atom interaction causes a frequency-dependent change to both the real and imaginary index of refraction. Unlike the other terms, though, the TOPE interaction causes a change which is direction-dependent. Therefore, there would be a direction-dependent change in the optical path length, which would show up as a differential cavity phase shift. The large cavity-finesse both amplifies the phase shift and increases the precision with which it can be detected. The differencing technique effectively subtracts common-mode laser frequency and mechanical noise.

 

Experimentally, after tuning the ring cavity to the edge of a resonance, we would search for a change in the differential cavity transmission as a function of static electric field direction. It appears that the statistical resolution on the phase shift DIFFERENCE of this system can approach the nanohertz per root hertz level, while principal sources of systematic errors (for example, effect of geometric misalignment of vectors in conjunction with the hyperfine interaction) appear to be acceptably small at the expected level of precision. Such a measurement, which uses the existing atomic beam, laser system, and high-voltage system, has the potential to surpass all other direct searches for this class of symmetry-violating interactions.