ISR precision measurements of the 2 pi cross section below 1 GeV with the KLOE experiment and their impact on (g-2)_mu

During the last 10 years, the use of initial state radiation (ISR) has changed from being a novel method to an established technique for precision measurements of hadronic cross sections at e+e- -colliders. By means of a dispersion integral, these measurements enter the hadronic contribution to the theoretical value of the anomalous magnetic moment of the muon, which still shows a 2-3sigma discrepancy with the experimental value measured at the Brookhaven National Laboratory.

The KLOE collaboration, operating the KLOE experiment at the DAPHNE e+e- -collider in Frascati, has published 4 measurements of the cross section for the process e+e- ->pi+pi- in the energy region below 1 GeV, covering ~70% of the total hadronic contribution to the muon anomaly.

I will present the ISR method in detail using the KLOE measurements as examples, and show how these measurements contribute to the current status of the theoretical evaluation of (g-2)mu.