Mainz 2012 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 54: Hadronenstruktur und -spektroskopie

HK 54.1: Group Report

Friday, March 23, 2012, 11:00–11:30, RW 1

Hadron physics with WASA-at-COSY — •Patrick Wurm — Institut für Kernphysik and Jülich Center for Hadron Physics, Forschungszentrum Jülich, Germany

The Wide Angle Shower Apparatus (WASA) is a close to 4π detector which is used to study the hadronic production and the decays of light mesons. Extended beam times at high luminosities enable to measure rare meson decays, which are used to scrutinize symmetries and symmetry breaking mechanisms in hadronic systems and to test Chiral Perturbation Theory, for example with η → π⁺ π⁻ π⁰ and η → π⁺ π⁻ γ. The electron and pion decay plane of the decay η → π⁺ π⁻ e⁺ e⁻ is sensitive to a possible flavor conserving CP violation. A better understanding of the hadron structure can be achieved by a precise determination of transition form factors, which can be measured in the decays η → e⁺ e⁻ γ, η → e⁺ e⁻ e⁺ e⁻ or ω → π⁰ e⁺ e⁻. Additionally, the branching ratio of η → e⁺ e⁻ e⁺ e⁻ is measured, since there exists currently only one experimental value. Signs for new physics beyond the Standard Model is searched for in π⁰ and η decays into a single lepton pair. The talk will give an overview of these WASA-at-COSY activities and also about other topics like the ABC effect.