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Search for eta-mesic He-4 in the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) reactions with the WASA-at-COSY facility
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics. Eberhard Karls Univ Tubingen, Phys Inst, Morgenstelle 14, D-72076 Tubingen, Germany.;Johannes Gutenberg Univ Mainz, Inst Kemphys, Johann Joachim Becher Weg 45, D-55128 Mainz, Germany..
Natl Ctr Nucl Res, Dept Nucl Phys, ul Hoza 69, PL-00681 Warsaw, Poland..
Jagiellonian Univ, Inst Phys, Prof Stanislawa Lojasiewicza 11, PL-30348 Krakow, Poland..
Univ Edinburgh, Sch Phys & Astron, James Clerk Maxwell Bldg,Peter Guthrie Tait Rd, Edinburgh EH9 3FD, Midlothian, Scotland..
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2017 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 959, p. 102-115Article in journal (Refereed) Published
Abstract [en]

The search for He-4-eta bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the dd -> (3)Hen pi(0) and dd -> (3)Hep pi(-) processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd -> He-4 eta reaction ranging from Q = 70 MeV to Q = 30 MeV. The luminosity was determined based on the dd -> (3)Hen reaction and the quasi-free proton proton scattering via dd -> ppn(spectator)n(spectator) reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in dd -> (4He-eta)(bound) -> (3)Hen pi(0) and dd -> (He-4-eta)(bound) -> (3)Hep pi(-) processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N* (1535) momentum distribution in the anticipated mesic-He-4. Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in He-4, we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for n pi(0) and p pi(-) channels, respectively. However, based on the recent theoretical findings of the N*(1535) momentum distribution in the N*-He-3 nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n pi(0) and p pi(-) channels respectively. (C) 2017 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV , 2017. Vol. 959, p. 102-115
Keywords [en]
eta-Mesic nuclei, eta meson
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:uu:diva-320871DOI: 10.1016/j.nuclphysa.2017.01.001ISI: 000395211400007OAI: oai:DiVA.org:uu-320871DiVA, id: diva2:1091172
Funder
EU, European Research CouncilAvailable from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-04-26Bibliographically approved

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Adlarson, PatrikCalén, HansFransson, KjellHeijkenskjöld, LenaJohansson, TordKupsc, AndrzejMarcinievski, PawelPszczel, DamianPyszniak, AndrzejZlomanczuk, Jozef

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Adlarson, PatrikCalén, HansFransson, KjellHeijkenskjöld, LenaJohansson, TordKupsc, AndrzejMarcinievski, PawelPszczel, DamianPyszniak, AndrzejZlomanczuk, Jozef
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