Dr Federico Nguyen (INFN Sezione Roma TRE)
The KLOE experiment, operating at the Frascati phi-factory DAPHNE, has measured the differential cross section for the process e+ e- --> pi+ pi- gamma as a function of the pi+pi- invariant mass, M(pipi). From the measured differential $M(pipi) spectrum inclusive of final state radiation, the total sigma(pi+pi-(gamma)) cross section is determined using the QED radiator function. The final result of the analysis of events with Initial State Radiation (ISR) photons emitted at small angle is presented, from a sample corresponding to an integrated luminosity of 240 pb-1 of data taken on peak of the phi meson. From the sigma(pi+pi-(gamma)) cross section, the pi-pi contribution to the muon magnetic anomaly is obtained in the mass range ( 0.592 < M(pipi) < 0.975 ) GeV with a statistical error of 0.1%, an experimental systematic error of 0.6% and a theoretical systematic error of 0.6%. Preliminary results from an independent analysis of events with an ISR photon detected at large angle are presented, from a sample corresponding to an integrated luminosity of 230 pb-1 of data taken off the phi peak. This selection allows to reach the pipi threshold with suppressed background from phi decays.
Simona Giovannella (INFN Frascati)