Study of Neutral-Pion Pair Production in Two-Photon Scattering at BESIII

Institute for Nuclear Physics, Johannes Gutenberg-Universität Mainz

^* e-mail: lellmann@uni-manz.de

Published online: 25 September 2024

Abstract

The anomalous magnetic moment of the muon, a_μ = (g−2)_μ/2, is one of the most precisely measured observables of the Standard Model. However, its value shows a sizeable discrepancy to the Standard Model prediction. It is still under discussion whether this discrepancy is a hint for New Physics or proof of the limited understanding of strong interaction at low energies. To get a better understanding of this discrepancy, one needs to reduce the uncertainty of both, the Standard Model prediction and the direct measurement.

Information on the production of pion pairs in two-photon fusion processes plays an important role in the dispersive calculation of the hadronic light-by-light scattering contribution to a_μ, which is one of the two large contributions to the Standard Model predictions uncertainty. The BESIII experiment, located at the Institute of High Energy Physics in Beijing/China, offers a perfect testbed for the investigation of two-photon processes at small momentum transfers. The process e⁺e⁻ → e⁺e⁻π⁰π⁰ is measured at the BESIII experiment at center-of-mass energies between 3.77 and 4.59 GeV with a total integrated luminosity of more than 13 fb⁻¹, with more data being available in future. This presentation will discuss the current status of the analysis.