Heidelberg 2015 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 28: Hadron Structure and Spectroscopy 6
HK 28.4: Talk
Tuesday, March 24, 2015, 15:30–15:45, T/SR25
Towards a new upper limit for the η-decay η→π0 + e+ + e− with WASA-at-COSY* — •Florian Bergmann, Kay Demmich, Nils Hüsken, Karsten Sitterberg, and Alfons Khoukaz for the WASA-at-COSY collaboration — Institut für Kernphysik, WestfälischeWilhelms-Universität Münster, Germany
A major part of the WASA-at-COSY experimental program is dedicated to investigations on symmetries and symmetry breaking to get a better understanding of the physics within the standard model. An elegant way to search for violation of conservation laws, which are directly connected to symmetry breaking effects, is the study of rare meson decays. Here the η-meson is of particular interest. High statistics of η-meson production are required to obtain new limits on the C, P and T symmetry breaking or combinations thereof. The study of rare meson decays also allows to search for physics beyond the standard model like the dark photon.
In this contribution we will present and discuss investigations of the C-violating η-decay η→π0 + e+ + e− using the high statistics p+d→3He+η data obtained with WASA-at-COSY. The dominant C-conserving contribution to this decay via a π0+γ*+γ* intermediate state has an expected branching ratio of less than 10−8 in the standard model. An observation of a significantly higher branching ratio would indicate the presence of a C-violating process. 1em *Supported by FFE program of the Forschungszentrum Jülich.