Search for the η-mesic 4He with WASA-at-COSY
1 M. Smoluchowski Institute of Physics, Jagiellonian University, 30-059 Cracow, POLAND
2 IKP, Forschungszentrum Jülich, D-52425 Jülich, GERMANY
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Published online: 20 March 2014
We conduct a search for the He − η bound state with the WASA-at-COSY facility measuring the excitation functions for the reaction channels: dd → 3Hepπ− and dd → 3Henπ0, where the outgoing N − π pairs originate from the conversion of the η meson on a nucleon inside the He nucleus. Two dedicated experiments were performed at the Cooler Synchrotron COSY-Jülich with the WASA detector. The analysis of the 2008 data shows no signal of the 4He − η bound state. An upper limit for the cross-section for the bound state formation and decay in the process dd → (4He − η)bound → 3Hepπ−, was determined at the 90 % confidence level. In November 2010 a new data set was collected.
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