Measurement of the e+e- › ?+?- cross section between 600 and 900 MeV using initial state radiation

Abstract

We extract the e+e-›?+?- cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb-1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor |F?|2 as well as the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to (g-2)µ. We find this value to be View the MathML source, which is between the corresponding values using the BaBar or KLOE data.