Frankfurt 2014 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 23: Hadronenstruktur und -spektroskopie

HK 23.7: Vortrag

Dienstag, 18. März 2014, 18:30–18:45, HZ 1+2

IN SEARCH OF THE BOX ANOMALY BY STUDYING η → π⁺ π⁻ γ — •Lersch Daniel for the WASA-at-COSY collaboration — Jülich Center for Hadron Physics, Forschungszentrum Jülich, Germany

The decay η→ π⁺ π⁻ γ is a suitable tool to study QCD anomalies. At the chiral limit, this decay is solely driven by the box anomaly term, which is part of the Wess-Zumino-Witten-(WZW) Lagrangian. However, at non zero meson masses, the triangle anomaly (also part of the WZW Lagrangian) dominates the box anomaly, because of the final state interactions between the two pions. Thus, a correct theoretical description of this decay can only be achieved by including final state interactions.
The experimental observables to test the interaction models are either the branching (done by CLEO and KLOE) or the distribution of the single photon energy, which has been recently measured in the reaction pd→ ³He[η→ π⁺π⁻γ] with WASA-at-COSY.
The aim of this work is to measure the branching ratio and the single photon energy distribution in one experiment using the reaction: pp→ pp[η→ π⁺π⁻γ]. The data have been acquired during an 8 week experiment in spring 2010.
First results will show, how the channel η→π⁺π⁻γ is selected and how the experimental observables are determined afterwards.