Precise Measurement of Parity Nonconserving Optical Rotation in Atomic Thallium

Abstract

We report a new measurement of parity nonconserving (PNC) optical rotation on the ${6p}_{1/2}$- ${6p}_{3/2}$ transition in atomic thallium near 1283 nm. The result expressed in terms of the quantity $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{Im}{{E1}^{\mathrm{PNC}}/M1}$ is $\ensuremath{-}(15.68\ifmmode\pm\else\textpm\fi{}0.45)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, and is consistent with current calculations based on the standard model. In addition, limits have been set on the much smaller nuclear spin-dependent rotation amplitude at ${R}_{S}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(0.04\ifmmode\pm\else\textpm\fi{}0.20)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}8}$; this is consistent with theoretical estimates which include a nuclear anapole contribution.