e+e− results from BaBar and their impact on the muon g−2 prediction

The BaBar collaboration has nearly completed a program of precise measurements of the cross sections for the dominant channels of from threshold to 3 GeV using the initial-state radiation (ISR) method, i.e. the measurement of the cross sections with the energetic γ detected at large angle to the beams. These data are used as input to vacuum polarization dispersion integrals, in particular the hadronic contribution to the muon g−2 anomaly. In addition to the recently measured π+π− and K+K− cross sections, giving the dominant contribution, multihadronic channels have been investigated, with some recent examples presented here for the π+π−π+π−, K+K−ππ, KSKL, KSKLπ+π−, KSKSπ+π− channels. The BaBar results have the best precision and cover for the first time almost all significant hadronic contributions below 2 GeV entering the muon g−2 prediction.