Yuki Sue

10 April 2024
IPNS physics seminar

Abstract: Current measurements and theoretical predictions of the muon anomalous magnetic moment a_mu disagree. Theoretical predictions on hadronic vacuum polarization corrections to a_mu are based on dispersive relations that require measurements of e+e- to hadron cross sections as inputs. The uncertainties on these measurements are the largest source of uncertainty on the prediction. The three-pion cross section is the second largest contribution to the hadronic vacuum polarization (HVP) of the muon anomalous magnetic moment. We report a measurement of the e+e- → pi+pi-pi-0 cross section in the energy range from 0.62 GeV to 3.50 GeV. The e+e- data sample used in the measurement was collected at or near the Upsilon(4S) resonance with the Belle II detector at the SuperKEKB collider, corresponding to 191 fb^{-1} of integrated luminosity. The uncertainty on the cross section at the omega and phi resonances is dominated by the systematic uncertainty of 2.2%. The corresponding contribution to a_mu is (48.91 +- 0.21 (stat)+-1.07 (syst))x10^-10.