Atomic parity violation as a probe of new physics

Abstract

Effects of physics beyond the standard model on electroweak observables ares studied using the Peskin-Takeuchi isospin-conserving, S, and -breaking, T, parametrization of ``new'' quantum loop corrections. Experimental constraints on S and T are presented. Atomic parity-violating experiments are shown to be particularly sensitive to S with existing data giving S=-2.7\ifmmode\pm\else\textpm\fi{}2.0\ifmmode\pm\else\textpm\fi{}1.1. That constraint has important implications for generic technicolor models which predict S\ensuremath{\simeq}0.1${\mathit{N}}_{\mathit{T}}$${\mathit{N}}_{\mathit{D}}$ (${\mathit{N}}_{\mathit{T}}$ is the number of technicolors, ${\mathit{N}}_{\mathit{D}}$ is the number of technidoublets).