Measurement of the pion form factor for M2ππ between 0.1 and 0.85 GeV2 with the KLOE detector

Abstract

The KLOE experiment at the ϕ-factory DAΦ has measured the pion form factor in the range between 0.1 < M2ππ < 0.85 GeV2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the M2ππ region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of Δaμππ = (478.5±2.0stat±4.8syst±2.9theo) · 10−10 further confirms the discrepancy between the Standard Model evaluation for aμ and the experimental value measured by the (g-2) collaboration at BNL.