Measurement of the hadronic cross section at KLOE/KLOE-2

Abstract

The measurement of the hadronic cross section σ(e+ e− → π+ π−) is particularly important to test the Standard Model calculation for the (g − 2) of the muon, where a long standing 3σ discrepancy is observed. Different measurements of this quantity have been performed at DAΦNE, the Frascati ϕ factory, with the KLOE detector. In 2005, 2008, 2013 the KLOE/KLOE-2 Collaborations published three measurements of the σ(e+ e− → π+ π−) cross section with the photon emitted at small angle, and an independent measurement of the σ(e+ e− → π+ π−) cross section with the photon emitted at large angle using data at a collision energy of 1 GeV (i.e. 20 MeV below the ϕ -peak) was published in 2010. In the following the preliminary combination of the last three KLOE results (KLOE08, KLOE10, KLOE12), together with the preliminary fit to the pion form factor, will be presented.