Ricerc@Sapienza

The three precision measurements of the cross section σ(e + e − → π + π − ) using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations.

Using 1.63 fb −1 of integrated luminosity collected by the KLOE experiment about 7 × 10 4 K S → π ± e ∓ ν decays have been reconstructed. The measured value of the charge asymmetry for this decay is A S = (−4.9 ± 5.7 stat ± 2.6 syst ) × 10 −3 , which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives A S = (−3.8 ± 5.0 stat ± 2.6 syst ) × 10 −3 and, together with the asymmetry of the K L semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance.