Abstract
The BESⅢ Collaboration has recently embarked on a two-photon physics program. Its main motivation is given by the large uncertainty of the contribution of hadronic light-by-light scattering to the anomalous magnetic moment of the muon αμ, and the need of electromagnetic transition form factors(TFF) as experimental input to improve the calculations. Data acquired with the BESⅢ detector at center-of-mass energies from 3.77 to 4.6 GeV allow for the determination of TFFs of light pseudoscalar mesons. The measurements are performed with a single-tag technique and result in unprecedented accuracy at momentum transfers below 2 GeV2, the region of highest importance for the calculations of αμ. Employing the same approach, the first double-tagged measurement of the pion transition form factor has been started. It is the first step towards a model independent parameterization of the TFF of the π0. Additionally, measurements of multi-meson final states have been engaged.
Abstract
The BESⅢ Collaboration has recently embarked on a two-photon physics program. Its main motivation is given by the large uncertainty of the contribution of hadronic light-by-light scattering to the anomalous magnetic moment of the muon αμ, and the need of electromagnetic transition form factors(TFF) as experimental input to improve the calculations. Data acquired with the BESⅢ detector at center-of-mass energies from 3.77 to 4.6 GeV allow for the determination of TFFs of light pseudoscalar mesons. The measurements are performed with a single-tag technique and result in unprecedented accuracy at momentum transfers below 2 GeV2, the region of highest importance for the calculations of αμ. Employing the same approach, the first double-tagged measurement of the pion transition form factor has been started. It is the first step towards a model independent parameterization of the TFF of the π0. Additionally, measurements of multi-meson final states have been engaged.
Open Access
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