Search for eta-mesic He-4 with the WASA-at-COSY detector

P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, T. Bednarski, F. S. Bergmann, M. Berlowski, H. Bhatt, M. Buescher, H. Calen, H. Clement, D. Coderre, E. Czerwinski, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. FoehlK. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C. -O. Gullstrom, F. Hauenstein, L. Heijkenskjold, V. Hejny, F. Hinterberger, M. Hodana, B. Hoistad, A. Jany, B. R. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F. A. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Klos, M. Krapp, W. Krzemien, P. Kulessa, A. Kupsc, K. Lalwani, L. Li, WASA COSY Collaboration

Research output: Contribution to journalArticlepeer-review


An exclusive measurement of the excitation function for the dd -> (3)Hep pi(-) reaction was performed at the Cooler Synchrotron COSY-Julich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 to 2.400 GeV/c crossing the kinematic threshold for the eta-meson production in the dd -> He-4 eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the He-4-eta system varied from -51.4 to 22 MeV. The integrated luminosity in the experiment was determined using the dd -> (3)Hen reaction. The shape of the excitation function for the dd -> (3)Hep pi(-) reaction was examined. No signal of the He-4-eta bound state was observed. An upper limit for the cross section for the bound state formation and decay in the process dd -> (He-4-eta)(bound) -> (3)Hep pi(-) was determined on the 90% confidence level and it varies from 20 to 27 nb for the bound state width ranging from 5 to 35 MeV, respectively. DOI: 10.1103/PhysRevC.87.035204

Original languageEnglish
Article number035204
Number of pages7
JournalPhysical Review C
Issue number3
Publication statusPublished - 8 Mar 2013



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