Hadronic Contributions to the Photon Vacuum Polarization and their Role in Precision Physics

Abstract

I review recent evaluations of the hadronic contribution to the shift in the fine structure constant and to the anomalous magnetic moment of the muon. Substantial progress in a precise determination of these important observables is a consequence of substantially improved total cross section measurement by the CMD-2 and BES II collaborations and an improved theoretical understanding. Prospects for further possible progress is discussed.Comment: 17 pages 7 figures 2 tables, update: incl. CMD-2 data, reference