| 1. |
- Adlarson, Patrik, et al.
(författare)
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Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
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Tidskriftsartikel (refereegranskat)abstract
- We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn -> d pi(0)pi(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t- channel Delta Delta process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m = 2.37 GeV, Gamma approximate to 70 MeV and I(J(P)) = 0(3(+)) in both pn and Delta Delta systems. Necessary further tests of the resonance interpretation are discussed.
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| 2. |
- Bashkanov, M., et al.
(författare)
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WHAT IS THE NATURE OF THE ABC EFFECT?
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 627-629
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Tidskriftsartikel (refereegranskat)abstract
- The ABC effect - an intriguing low-mass enhancement in the pi pi invariant mass spectrum - is known from inclusive measurements of two-pion production in nuclear fusion reactions. Exclusive measurements have been carried out at CELSIUS/WASA and WASA-at-COSY for the fusion reactions leading to d, (3)He and (4)He. They all reveal this effect to be of isoscalar nature and associated with a narrow Lorentzian-shaped structure in the total cross section. The latter could point to the formation of an isoscalar resonance, which couples to the pn channel as well as to an intermediate Delta Delta state.
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| 3. |
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| 4. |
- Berlowski, Marcin, et al.
(författare)
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SEARCH FOR EXOTIC EFFECTS IN eta MESON LEPTONIC DECAYS
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 630-631
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Tidskriftsartikel (refereegranskat)abstract
- The search for the decay eta -> e(+)e(-) was carried out using the WASA detector at the COSY storage ring. Data were taken during a two week experimental run in Sept-Nov 2008 in which about 10(7) eta mesons were collected from the reaction of pp -> pp eta at energy of 1.4 GeV. Background studies were performed for several different reactions. The performance of the WASA detector for the measurement of electron-positron pairs based on the single Dalitz decay of the eta meson was studied. We also identified a statistically significant data sample of other more frequent leptonic decays.
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| 7. |
- Hejny, Volker, et al.
(författare)
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CHARGE SYMMETRY BREAKING IN dd -> (4)He pi(0) WITH WASA-at-COSY
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 595-597
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Tidskriftsartikel (refereegranskat)abstract
- Charge symmetry breaking effects can be used as an experimental tool to study quark mass effects. Using recent high precision data from TRIUMF and IUCF an international theory collaboration is working on a consistent description within the framework of chiral pertubation theory. The WASA-at-COSY collaboration has started an experimental program extending the studies on the reaction dd -> (4)He pi(0) towards higher excess energies in order to provide necessary information on the contribution of p-waves. First preliminary results on the total cross section at Q = 60 MeV are presented.
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| 8. |
- Hodana, Malcorzata, et al.
(författare)
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STUDY OF THE eta -> gamma e(+)e(-) DECAY WITH THE WASA-at-COSY
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 650-651
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Tidskriftsartikel (refereegranskat)abstract
- In October 2008, the WASA-at-COSY collected more than 10(7) events for the pd -> (3)He eta reaction. The aim is the determination of the invariant mass of the lepton pairs created in the Dalitz decay eta -> gamma e(+)e(-). The e(+)e(-) invariant mass spectrum is directly related to the distribution of the four-momentum squared of the virtual photon from the eta -> gamma gamma* process and hence it allows for the study of the transition form factor which in turn reflects the structure of the decaying meson.
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| 9. |
- Jany, Anna, et al.
(författare)
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STUDIES OF MESON PRODUCTION AND DECAYS IN pd -> (3)He X WITH WASA-at-COSY
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 652-653
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Tidskriftsartikel (refereegranskat)abstract
- Studies of meson production in the pd -> (3)He X reaction, where X = eta, eta' and omega, and their decays are investigated with the WASA-at-COSY facility. The angular distribution of the eta in the center of mass of the (3)He-eta system, have been measured at an excess energy of Q = 61 MeV over the full angular range. The anisotropy expected at the relatively large Q is observed.
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