Parity Nonconservation In Zero Momentum Transfer Lepton Hadron Interactions (hydrogen Atom, Violation).

Abstract

We are performing an experiment with a lepton-hadron bound state system which yields an upper limit on parity nonconservation in the electron-proton interaction. We measure electric dipole transition rates between perturbed hyperfine states of metastable H(2S). The primary effect of a PNC electron-proton interaction is to mix S and P states. Since a transition electric dipole moment, E1(,PNC), induced by such an interaction is expected to be extremely small, we have designed an experiment to observe it in interference with a parity-conserving (PC) electric dipole amplitude, E1(,PC), induced by the Stark effect, in a transition region which breaks inversion symmetry. We observe microwave (f (TURNEQ) 1600 MHz) electric dipole transitions between the Zeeman hyperfine substates (alpha)(,o) and (beta)(,o) of H(2S) in a dc electric field ((')E) and a dc magnetic field ((')B) set near the level crossings of the (beta) substates and the substates e of the strong damped 2P(, 1/2) state. The detected final state is (beta)(,o) as it is the only state at this level crossing which is mixed with a nearby P state ((epsilon)(,o)) by the PNC interaction. The microwave electric field, (epsilon), and (')E and (')B are arranged in a configuration which breaks inversion symmetry. The PNC term changes sign under a reversal of the directions of (')E and (')B, or (epsilon)(,x), corresponding to reversals of the handedness of the transition region. Significant redesign of the apparatus and the addition of an NMR based magnetic field control unit has resulted in a generation of the experiment in which all three flips can be utilized. The (epsilon)(,x) reversal is performed while the system is under vacuum by rotating the microwave cavity 180(DEGREES) about an axis tilted 5(DEGREES) with respect to its cylindrical axis. The electric field reversal is performed by applying alternating voltages to two closely-spaced carbon-coated glass semicylinders located inside the microwave cavity. At this time we have demonstrated that this method of applying electric fields will drive a transition with minimal distortion to the microwave field. An NMR unit assures the constancy of the magnitude of the magnetic field when it is reversed.