Update of the hadronic contribution to the QED vacuum polarization

摘要

We have updated the evaluation of the hadronic contribution to the running of the QED fine structure constant. It is obtained from a dispersion integral over a parametrization of the measured cross section of e(+)e(-) hadrons. We find this contribution to be Delta alpha ((5))(had)(s) = 0.02761 +/- 0.00036 at s = m(2) corresponding to 1/alpha ((5)) (m(Z)(2)) = 128.936 +/- 0.046. The improved experimental accuracy is mainly due to recent BES measurements. We have also updated and parametrized the hadronic contribution to Ce as a function of energy. (C) 2001 Elsevier Science B.V. All rights reserved. References: 32