Measurement of sigma-(e(+)e(-) -> pi(+)pi(-)) from threshold to 0.85 GeV2 using initial state radiation with the KLOE detector

We have measured the cross section of the radiative process e(+)e(-) -> pi(+)pi(-)gamma with the KLOE detector at the Frascati phi-factory DA(1)NE, from events taken at a CM energy W =1 GeV. Initial state radiation allows us to obtain the cross section for e(+)e(-) -> pi(+)pi(-), the pion form factor vertical bar F-pi vertical bar(2) and the dipion contribution to the muon magnetic moment anomaly, Delta alpha(pi pi)(mu) = (478.5 +/- 2.0(stat) +/- 5.0(syst) +/- 4.5(th)) x 10(-10) in the range 0.1 < M-pi pi(2) <0.85 GeV2, where the theoretical error includes a SU(3) chi PT estimate of the uncertainty on photon radiation from the final pions. The discrepancy between the Standard Model evaluation of alpha(mu) and the value measured by the Muon g-2 collaboration at BNL is confirmed. (C) 2011 Elsevier B.V. All rights reserved.