Measurement of the pion form factor for M_{pipi}^2 between 0.1 and 0.85 GeV^2 with the KLOE detector

Abstract

The KLOE experiment at the phi-factory DA$\Phi$NE has measured the pion form factor in the range between 0.1 < M_{pipi}^2 < 0.85 GeV^2 using events taken at sqrt{s}= 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the M_{pipi}^2 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 Δa_mu^{pipi} = (478.5+-2.0_{stat}+-4.8_{syst}+-2.9_{theo}) 10^{-10} further confirms the discrepancy between the Standard Model evaluation for a_mu and the experimental value measured by the (g-2) collaboration at BNL.

6 pages, 9 figures, to appear in the Proceedings of the PHIPSI09 Workshop, Oct 13-16, 2009, Beijing, China