Parity Nonconservation in Relativistic Hydrogenic Ions

Hydrogenic systems are attractive objects for precision measurements of parity nonconservation (PNC) since their simple atomic structure allows for accurate theoretical calculations necessary for relating the observed effects to the standard model. Various possibilities for PNC experiments with hydrogenic ions have been discussed in the literature. Most of the early work dealt with the PNC contribution to the 2S ! 1S 1 1g spontaneous decay [1,2] (an experimental upper limit on PNC mixing in hydrogenlike argon was obtained in [3]), while PNC in transitions between metastable states [4,5] was discussed more recently. Unfortunately, none of the possibilities discussed in these papers seem to offer realistic ways to observe PNC effects, much less to achieve the high precision desirable today. Here, we show that high precision PNC experiments with ions become possible, in view of recent developments in relativistic ion colliders, high-brightness ion sources, laser cooling methods of ions in storage rings, etc. In particular, PNC experiments in relativistic hydrogenic ions involving laser-induced 1S 1 1g ! 2S transitions can be carried out using the heavy ion accelerators RHIC, SPS, and LHC. Relativistic Doppler tuning is used to tune laser light (photon energy , a few eV) in resonance with the ion transition (,keV in the ion rest frame) also allowing laser cooling, and polarization of ions by optical pumping. It is estimated that the PNC effect can be measured with statistical uncertainty ,1023 in about a week of running time. At this level, these measurements provide a quantitative test of the standard model sensitive to its various possible extensions [6]. We consider the conceptually simplest variant of a PNC experiment in a hydrogenic system: circular dichroism on the 1S ! 2S transition in the absence of external electric and magnetic fields. Dichroism arises due to interference between the M1 and the PNC-induced E1 amplitudes of the transition. This approach allows one to estimate the required ion beam and laser parameters, and the achievable statistical sensitivity. In practice, it will be necessary to use one of the schemes involving ion polarization and external electric and magnetic fields [2]. These schemes do not change statistical sensitivity in an idealized experiment. In practice, however, they