Two-pion contribution to hadronic vacuum polarization

A bstract We present a detailed analysis of e + e − → π + π − data up to $$ \sqrt{s}=1 $$ s=1 GeV in the framework of dispersion relations. Starting from a family of ππ P -wave phase shifts, as derived from a previous Roy-equation analysis of ππ scattering, we write down an extended Omnès representation of the pion vector form factor in terms of a few free parameters and study to which extent the modern high-statistics data sets can be described by the resulting fit function that follows from general principles of QCD. We find that statistically acceptable fits do become possible as soon as potential uncertainties in the energy calibration are taken into account, providing a strong cross check on the internal…

• NS
  National Science Foundation
• UD
  U.S. Department of Energy

  Awards: FG02-00ER41132, -SC0009919, DE-FG02-, DE-FG02-00ER41132, DE-SC0009919, DE-FG02
• UO
  University of Washington
• SN
  Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung

  Awards: P300P2, 167751