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HK: Fachverband Physik der Hadronen und Kerne

HK 8: Fundamental Symmetries I

HK 8.1: Gruppenbericht

Montag, 30. März 2020, 16:30–17:00, J-HS B

Inputs to the Hadronic Contributions to (g−2)_µ from BESIII — •Christoph Florian Redmer and Achim Denig — Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany

The Standard Model prediction of the anomalous magnetic moment of the muon a_µ=(g−2)_µ/2 is limited by its hadronic contributions, due to the non-perturbative nature of the strong interaction at the relevant energy scales. In order to establish the significance of the long standing discrepancy between the direct measurement and the prediction of currently three to four σ, both, experiment and theory, need to be improved. Recently developed data driven approaches allow to make use of related information obtained in precision measurements to reduce the uncertainties of the Standard Model prediction of a_µ.

The BESIII collaboration embarked on a dedicated experimental program of hadronic cross section and transition form factor measurements to provide inputs to the calculations. The large data samples acquired at center of mass energies at and above the ψ(3770) peak allow to determine exclusive hadronic cross sections with high accuracy at energies below 2 GeV using the technique of initial state radiation. The single-tagged investigation of two-photon processes allows to measure transition form factors of light pseudoscalar mesons and meson systems in the range of momentum transfers, which is most relevant to the a_µ calculations.

In this presentation we discuss recent results, ongoing projects, and the prospects of the efforts at BESIII — Supported by DFG SFB1044.