Erlangen 2026 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 3: Hadron Structure and Spectroscopy II
HK 3.7: Talk
Monday, March 16, 2026, 18:00–18:15, PHIL A 401
Polarization in the two-photon production of pion pairs and how to use it — •Max Lellmann, Achim Denig, Jan Muskalla, and Christoph Florian Redmer — Johannes Gutenberg Universität Mainz
The accuracy of the Standard Model prediction for the hadronic light-by-light contribution to the muon’s anomalous magnetic moment aµ is strongly limited by the knowledge of two-photon couplings of axial and tensor mesons. The coupling of the lightest tensor state, f2(1270), can be conveniently studied in the process e+e− → e+e− π0π0, in which the pion pair is produced through the fusion of two virtual photons emitted by the leptons.
A reliable extraction of the tensor state’s two-photon coupling requires proper corrections for reconstruction efficiency and other detector effects, which in turn demand accurate Monte Carlo simulations of the process. By implementing such a generator that, for the first time, includes a fully exclusive description of the e+e− → e+e− π0π0 reaction, additional features of the cross section become accessible and can be used to extract further information from the same data.
This talk will outline the method and introduce the corresponding Monte Carlo generator, HadroTOPS.
Keywords: Monte Carlo; hadronic two-photon scattering; partial wave analysis; two-photon cross sections