R scan in 2-5 GeV with BESII at BEPC

Abstract:

With an upgraded Beijing Spectrometer (BESII) at the Beijing Electron
Positron Collider (BEPC), the BES collaboration finished an R scan in
the energy region from 2 to 5 GeV.  Preliminary R values for all 85
scanned energy points will be presented.  This measurement will make an
important contribution to the precision determination of
$\alpha{M_Z^2}$, the QED coupling constant evaluated at the Z pole.  The
present uncertainty is a serious limit to further progress in the
determination of the Higgs mass from radiative corrections in the
Standard Model.  The results can also contribute to the interpretation
of the muon g-2 measurement.