A Non Accelerator Probe of New Physics
Motion reversal is known in physics parlance as time-reversal,as it can be realised mathematically by changing time, t to - t.The origin of time-reversal violation is one of the least understood of all the profound issues in physics. The observation of an electric dipole moment (EDM) of any fundamental particle or of a composite system like an atom or a molecule is a direct signature of the violation of time-reversal symmetry in Nature.Open-shell atoms will have two dominant sources of intrinsic electric dipole moments; one due to the intrinsic EDM of its constituent electrons and the other due to a time-reversal violating interactionbetween the electrons and the nucleus mediated by spin zero particles. Despite the relentless experimental search for EDMs in elementary particles as well as in composite systems for more than five decades no conclusive result has been obtained. However, many on-going high precision atomic EDM experiments are aiming to achieve better detection limits, a few orders of magnitude lower than the current experimental limits. In order to obtain a limit for the electron EDM, one needs both the enhancement factors (ratios of the atomic to the electron EDMs) and the experimental atomic EDMs to a high precision. A rigorous relativistic quantum mechanical calculation has been carried out to predict the EDM enhancement factors for Rubidium (Rb) and Cesium (Cs) with a sub 1% accuracy for the first time. One of the unique features of this work is that it deals with the interplay of two very different interactions — the long-range Coulomb interaction and the short-range time-reversal violating interaction. The new results for the enhancement factors combined with those of the proposed non-accelerator EDM experiments on Rb and Cs, when they achieve their desired sensitivities, could open up a novel direction for finding new physics beyond the much celebrated model of particle physics, the Standard Model, indeed quite significant, in the era of the Large Hadron Collider. This could also serve as stringent tests of many unification models, including Super-symmetry, and provide insights into one of the most important but unresolved questions in cosmology: the matter-antimatter asymmetry in the Universe to which we owe our existence today.
The full text of the paper authored by H. S. Nataraj, B. K. Sahoo, B. P. Das and D. Mukherjee has been accepted for publication in The Physical Review Letters (arXiv source: http://arxiv.org/abs/0804.0998).
-- H.S. Nataraj
