Session B8: Invited Session: Search for New Physics with Atoms, Molecules and Nuclei

Tests of fundamental symmetries

``Fundamental symmetry'' refers to invariance of the laws of Nature, including the values of fundamental constants, with respect to a continuous or discrete transformation such as translation in space or time, rotation, spatial (P), time (T), or charge (C) reversal, combinations of these, or permutation of identical quantum particles. All discrete symmetries except for the combined CPT and the permutation symmetry are experimentally known to be violated by the weak interactions; intense searches are conducted for possible small violations of the still-standing discrete as well as the continuous symmetries, which may result from exotic beyond-the-standard-model interactions. In this talk, I will describe some of the recent fundamental-symmetry tests involving our research group (for up-to-date bibliography see http://budker.berkeley.edu/PubList.html), including measuring the effect of the gravitation-field gradient on the value of the fine-structure ``constant,'' and searching for transient and time-dependent effects on atomic magnetometers and clocks.   

Manifestations of Symmetry Violation in Nuclei

Nuclei are remarkable laboratories for testing symmetries, frequently greatly enhancing small effects through energy degeneracies and other means, and often selecting out specific interactions through selection rules imposed by angular momentum, isospin, and energetics. Some of our most stringent tests of time reversal invariance, lepton number conservation, and parity come from experiments done on atomic nuclei. I summarized the status of several such tests, and describe some of the questions that remain unresolved.   

New Upper Limit on the Electron's Electric Dipole Moment

The ACME collaboration has measured the electron's electric dipole moment (eEDM) to be $d_e = (-2.1 \pm 3.7_{\mathrm{stat}} \pm 2.5_{\mathrm{syst}}) \times 10^{-29} \; e \cdot \mathrm{cm}$ [1,2]. This corresponds to an upper limit of $|d_e| < 8.7 \times 10^{-29} \; e \cdot \mathrm{cm}$ with 90 percent confidence, which represents an order of magnitude improvement on the previous best limit [3]. We describe our method of measuring the eEDM using a buffer gas cooled beam of thorium monoxide (ThO) and discuss our approach to finding and quantifying systematic effects. This results constrains T-violating physics at the TeV energy scale.\\[4pt] [1] The ACME Collaboration, \emph{Science} \textbf{343}, (2014) 269--272.\\[0pt] [2] L.~V.~Skripnikov, A.~N.~ Petrov, and A.~V.~Titov, \emph{J.~Chem.~Phys.} \textbf{139}, (2013) 221103.\\[0pt] [3] J.~J.~Hudson, D.~M.~Kara, I.~J.~Smallman, B.~E.~Sauer, M.~R.~Tarbutt, and E.~A.~Hinds, \emph{Nature} \textbf{473}, (2011) 493--496.