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HK: Fachverband Physik der Hadronen und Kerne

HK 10: Hadron Structure and Spectroscopy II

HK 10.3: Vortrag

Dienstag, 31. August 2021, 15:00–15:15, H3

Small Angle ISR Analysis of the Pion Form Factor with BESIII — •Yasemin Schelhaas and Achim Denig for the BESIII collaboration — Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, Deutschland

The anomalous magnetic moment of the muon a_µ=(g_µ−2)/2 is one of the most precisely measured variables in modern physics. However, there is a discrepancy of 4.2 standard deviations between the Standard Model (SM) prediction and the experimental average of the latest direct measurements, known as the Muon (g−2)-puzzle. The main uncertainty of the SM prediction arises from hadronic contributions and can be improved systematically using experimental measurements of hadronic cross sections at e⁺ e⁻ colliders. One of the most important processes is e⁺ e⁻ → π⁺ π⁻. Using a data set of 3.1 fb⁻¹ at a center of mass energy of 4.18 GeV, the π⁺ π⁻ cross section is measured at the BESIII experiment located at the BEPCII collider in Beijing, exploiting Initial State Radiation (ISR) at small angles. The analysis aims to determine the pion form factor at masses above 0.8 GeV, which is also interesting for hadron spectroscopy. In this presentation an overview of the current status of the analysis is given.

Supported by DFG.