Abstract
A difference of more than three standard deviations between is currently observed between the direct experimental measurement and the Standard Model prediction of the anomalous magnetic moment of the muon (g−2)μ. The hadronic vacuum polarization contributions can be related to hadronic cross sections using the optical theorem. Precision measurements of the hadronic cross sections e+e−→π+π−, π+π−π0, π+π−2π0, ωπ0 and π+π−3π0 are performed at the BESIII experiment located in Beijing, China. The initial state radiation method is used to access the energy regions of interest for (g−2)μ. Our results will improve the precision of the Standard Model prediction of (g−2)μ.
Highlights
The anomalous magnetic moment of the muon has been measured several times
These cross section measurements are needed as input for the Standard Model prediction of the anomalous magnetic moment of the muon, (g − 2)μ.The initial state radiation method is used to access the energy regions of interest for (g − 2)μ
Both on the theory and the experimental side to see whether this deviation vanishes, or goes beyond five standard deviations, which would give good hints where to look for physics beyond the Standard Model
Summary
The anomalous magnetic moment of the muon has been measured several times. The E821 experiment at BNL [1] provided the latest and most precise measurement. The e+e− → π+π−π0 cross section can be measured with the BESIII measurement in the region of the ω and φ resonances using the tagged ISR technique. Untagged ISR methods are performed to measure the e+e− → π+π−π0 cross section. The e+e− → π+π−2π0 cross section is measured with both, the tagged and untagged ISR methods. The e+e− → π+π−3π0 and e+e− → π+π−3π0γISR processes are measured in order to correct the corresponding MC simulations With this data driven method, the accuracy and the systematic uncertainty of the background subtraction can be significantly reduced. The π+π−2π0 cross section combined from the tagged and untagged methodes, shown, is calculated according to Eq 1, from the selected π+π−2π0γISR events. The measured cross section is corrected for vacuum polarization effects and final state radiation effects.
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