From Hadronic Cross Section to the measurement of the Vacuum Polarization at KLOE: a fascinating endeavour

Abstract

The KLOE experiment at the ϕ-factory DAΦNE in Frascati is the first to have employed Initial State Radiation (ISR) to precisely determine the e+e− → π+π−(γ) cross section below 1 GeV. Such a measurement is particularly important to test the Standard Model (SM) calculation for the (g – 2) of the muon, where a long standing 3σ discrepancy is observed. I will review the ISR activity in KLOE in the last 20 years from the measurement of the hadronic cross section to the first direct determination of the time-like complex running α(s) in the region below 1 GeV.