Hadronic vacuum polarization effects in alpha_{em}(M_Z)

Abstract

Recent evaluations of the hadronic vacuum polarization contributions to the effective fine-structure constant alpha_{em}(M_Z) are summarized and commented. A new update based on corrected CMD-2 data is presented. My new estimates are Delta alpha_{had}^{(5)}(M_Z) = 0.027773 +/- 0.000354 (e^+e^- - data based) and Delta alpha_{had}^{(5)}(M_Z) = 0.027664 +/- 0.000173 (via the Adler-function and extended use of pQCD). Prospects of further possible progress is discussed.

Comments: 16 pages, Latex, 3 figures, 2 tables