Electric Dipole Moments of Atoms and the Neutron
An Electric Dipole Moment or EDM refers to a separation of charge along the angular-momentum axis of an atom or the neutron. An EDM arises due to forces that distinguish the handedness (parity) and direction of time, i.e. due to violation of Parity and Time Reversal. Over the past 50 years, a number of experiments have been devised to measure EDMs, but so far only upper limits have been set. But we have strong reason to expect EDMs: first, the well established Standard Model of elementary particle interactions provides two ways to produce and EDM - through the weak interaction mixing of quark generations and through a strong-interaction parameter - though the quark-mixing contribution is known to be extremely small compared to experimental sensitivities. the second reason to expect EDMs is that the same forces that induce EDMs would also produce the Cosmological Baryon Asymmetry. The Baryon Asymmetry is the small prevalence of matter over antimatter in the early universe that resulted in the excess of matter available to make the galaxies, stars, planets, etc. of the current universe. The Baryon Asymmetry could not arise from Standard Model physics, and thus the search for EDMs is the search for new, Beyond Standard Model physics. I will discuss what we can learn from EDM measurements past and future and focus on our neutorn-EDM efforts and experiments using noble gas atoms xenon and radon.
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