KLOE uses the radiative return to measure the hadronic cross section e(+)e(-) --> pi(+) pi(-) at DAPhiNE. The emission of one or more hard photons in the initial state (ISR) reduces the collision energy, otherwise fixed at 1020 MeV, and allows to perform an effective scan of the two pions invariant mass squared, s(pi), in the whole s(pi) region 2 from threshold to m.. An extremely accurate knowledge of experimental systematics, background, luminosity and, on the theoretical side, a precise description of initial state radiation are needed to perform a competitive measurement. We present here the status of the analysis of 140 pb(-1) collected in 2001. A preliminary evaluation of the hadronic contribution to a(mu) in the S-pi range between 0.37 GeV2 and 0.93 GeV2 yields a(mu) = 378.4 +/- 0.8(stat) +/- 4.5(syst) +/- 3-0(theo) 3.8(FSR), consistent with the CMD-2 result and confirming the present discrepancy between e(+)e(-) and tau data.
Aloisio, A., Ambrosino, F., Antonelli, A., Antonelli, M., Bacci, C., Bencivenni, G., et al. (2004). The hadronic cross section measurement at KLOE. NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS, 131, 75-81 [10.1016/j.nuclphysbps.2004.02.011].