SMuK 2021 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 10: Hadron Structure and Spectroscopy II

HK 10.1: Gruppenbericht

Dienstag, 31. August 2021, 14:00–14:30, H3

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

The long-standing discrepancy between Standard Model prediction and direct measurement of the muon anomalous magnetic moment a_µ=(g−2)_µ/2 has recently been confirmed by a new measurement by the Muon-g-2-collaboration at Fermilab. In order to establish the significance of the discrepancy between the prediction and direct measurement of currently 4.2σ, both, experiment and theory, need to be improved.

The Standard Model prediction of a_µ is limited by its hadronic contributions, due to the non-perturbative nature of the strong interaction at the relevant energy scales. A large contribution to the uncertainty of the Standard Model calculation stems from the hadronic light-by-light scattering contribution. Its accuracy depends heavily on the knowledge of transition form factors of light pseudoscalar mesons and the production of meson systems from two-photon collisions.

The BESIII experiment, a τ-charm-factory located at the Institute of High Energy Physics in Beijing, China, offers a perfect test bed for the investigation of two-photon processes in the momentum transfer range, which is most relevant to the a_µ calculations. In this presentation we discuss recent results, ongoing projects, and future prospects of the measurements of transition form factors at BESIII.