SMuK 2023 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 18: Hadron Structure and Spectroscopy II

HK 18.2: Vortrag

Dienstag, 21. März 2023, 17:30–17:45, SCH/A316

Testing Predictions of the Chiral Anomaly in Primakoff Reactions at COMPASS* — •Dominik Ecker and Andrii Maltsev for the COMPASS collaboration — Physik-Department, Technische Universität München

Chiral Perturbation Theory (ChPT) makes effective predictions for low-energy phenomena of QCD, i.e. dynamics and decays of light mesons, and their couplings to photons and nucleons. Processes, which are governed by the chiral anomaly, are described in the effective Lagrangian by the Wess-Zumino-Witten (WZW) term. The WZW term describes for example the coupling of one pion to two photons. Hence, it describes the π⁰ lifetime, which has been well confirmed by multiple measurements.

There are however many more couplings governed by the chiral anomaly, which lack precise experimental verification: for example, the direct coupling of one photon to three pions. The corresponding coupling constant F_3π is described by the WZW term and can experimentally be accessed in π⁻ + γ → π⁻ + π⁰ scattering reactions.

At the COMPASS experiment at CERN, we study pion-photon scattering reactions via the Primakoff effect. These data allow us to verify the ChPT prediction for F_3π. We will present preliminary result of this measurement and ongoing efforts to improve its accuracy.

*funded by the DFG under Germany’s Excellence Strategy - EXC2094 - 390783311 and BMBF Verbundforschung (05P21WOCC1 COMPASS).