| 1. |
- Adolph, C, et al.
(författare)
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Measurement of the eta -> 3 pi(0) Dalitz plot distribution with the WASA detector at COSY
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 677:1-2, s. 24-29
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Tidskriftsartikel (refereegranskat)abstract
- In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz plot of the three pious was Studied using 1.2 x 10(5) fully reconstructed events. and the quadratic slope parameter alpha was determined to be -0.027 +/- 0.008(stat) +/- 0.005(syst). The result is consistent with previous measurements and further corroborates the importance of pion-pion final state interactions. (C) 2009 Elsevier B.V. All rights reserved.
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| 2. |
- 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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| 3. |
- Tanaka, Y. K., et al.
(författare)
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Search for eta '-mesic nuclei using (p,d) reaction with FRS/Super-FRS at GSI/FAIR
- 2020
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1643
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Tidskriftsartikel (refereegranskat)abstract
- We plan a semi-exclusive measurement of the C-12(p,dp) reaction to search for eta'-mesic nuclei, aiming at investigating in-medium properties of the eta'-meson. We employ a 2.5 GeV proton beam impinging on a carbon target to produce eta'-mesic C-11 nuclei via the C-12(p,d)eta'circle times C-11 reaction. Using coincidence measurements of the forward going deuterons, important for missing-mass spectroscopy, and decay protons emitted from the eta'-mesic nuclei for event selection will provide a high experimental sensitivity to observe eta'-mesic nuclei. We will perform the measurements by combining the WASA detector system with the fragment separator FRS at GSI and also with the Super-FRS at FAIR in the future. The plan of the experiments and the present status are reported.
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| 4. |
- Wildner, E., et al.
(författare)
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The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex
- 2016
-
Ingår i: Advances in High Energy Physics. - : Hindawi Publishing Corporation. - 1687-7357 .- 1687-7365.
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Tidskriftsartikel (refereegranskat)abstract
- The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world's most powerful neutron source. The average power of the proton linac will be 5 MW. Pulsing this linac at higher frequency will make it possible to raise the average total beam power to 10 MW to produce, in parallel with the spallation neutron production, a very intense neutrino Super Beam of about 0.4 GeV mean neutrino energy. This will allow searching for leptonic CP violation at the second oscillation maximum where the sensitivity is about 3 times higher than at the first. The ESS neutrino Super Beam, ESSnuSB operated with a 2.0 GeV linac proton beam, together with a large undergroundWater Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5 sigma. significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section. The paper presents the outstanding physics reach possible for CP violation with ESSnuSB obtainable under these assumptions for the systematic errors. It also describes the upgrade of the ESS accelerator complex required for ESSnuSB.
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| 5. |
- Clement, H., et al.
(författare)
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Search for narrow NN-decoupled resonances in the πNN-system : An overview
- 1996
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Ingår i: Progress in Particle and Nuclear Physics. - : Elsevier BV. - 0146-6410 .- 1873-2224. ; 36, s. 369-378
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Tidskriftsartikel (refereegranskat)abstract
- The status of the search for NN-decoupled resonances in the πNN-system is reviewed. After a short survey on the history of dibaryon searches reactions suitable for detecting such resonances are discussed. Special emphasis is put on the pionic double charge exchange, where recently evidence for the signature of a narrow πNN resonance, called d′, with I(J P) = even (0 -) and m = 2.06 GeV has been quoted. Further reactions discussed in this context are the pion photoproduction on the deuteron and the two-pion production in nucleon-nucleon collisions.
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| 6. |
- Farabolini, W., et al.
(författare)
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Recent Results from CTF3 Two Beam Test Stand
- 2014
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Ingår i: Proceedings, 5th International Particle Accelerator Conference (IPAC 2014).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Saito, T. R., et al.
(författare)
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Studies of three-and four-body hypernuclei with heavy-ion beams, nuclear emulsions and machine learning
- 2023
-
Ingår i: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 2586
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Tidskriftsartikel (refereegranskat)abstract
- Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Lambda nn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.
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| 8. |
- Saito, T. R., et al.
(författare)
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The WASA-FRS project at GSI and its perspective
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 542, s. 22-25
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique to study bound states of exotic hadrons in subatomic nuclei, such as hypernuclei and mesic nuclei, has been developed by employing the Fragment Separator FRS and the WASA central detector at GSI. Two experiments, S447 for studying light hypernuclei, especially hypertriton and a Ann bound state, and S490 for searching for ri' mesic-nuclei, were recently performed. Data analyses are currently in progress, and light charged particles such as protons and x & PLUSMN; are clearly observed and identified in the both experiments. For S447, light nuclear fragments that can also be residual nuclei from decays of hypernuclei of interests have been analysed by the FRS, and a momentum resolution, Ap/p, of 5 x 10-4 has been achieved. Further data analyses are to be completed. The WASA-FRS project will be continued and extended with the FRS at FAIR Phase 0, and upgrading of the WASA magnet and detectors is currently in progress. Furthermore, construction of a larger detector system with the Super-FRS at FAIR Phase 1 is also under consideration.
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| 9. |
- Tanaka, Y. K., et al.
(författare)
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WASA-FRS EXPERIMENTS IN FAIR PHASE-0 AT GSI
- 2023
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Ingår i: ACTA PHYSICA POLONICA B PROCEEDINGS SUPPLEMENT. - : Jagiellonian University.
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Konferensbidrag (refereegranskat)abstract
- We have developed a new and unique experimental setup integrating the central part of the Wide Angle Shower Apparatus (WASA) into the Fragment Separator (FRS) at GSI. This combination opens up possibilities of new experiments with high-resolution spectroscopy at forward 0 and measurements of light decay particles with nearly full solid-angle acceptance in coincidence. The first series of the WASA-FRS experiments have been successfully carried out in 2022. The developed experimental setup and two physics experiments performed in 2022 including the status of the preliminary data analysis are introduced.
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| 10. |
- Akimov, D., et al.
(författare)
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Physics with WASA and PROMICE
- 1994
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Ingår i: Physics with GeV-particle beams, Juelich 1994. ; , s. 519-530
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Konferensbidrag (refereegranskat)
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| 11. |
- Bargholtz, Chr., et al.
(författare)
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Measurement of the eta -> pi(+)pi(-)e(+)e(-) decay branching ratio
- 2007
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 644:5-6, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- The reaction pd -> He-3 eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta -> pi(+)pi(-)e(+)e(-) is measured to be (4.3 +/- 1.3 +/- 0.4) x 10(-4).
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| 12. |
- Bargholtz, Chr., et al.
(författare)
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The WASA detector facility at CELSIUS
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 594:3, s. 339-350
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Tidskriftsartikel (refereegranskat)abstract
- The WASA 4 pi multidetector system, aimed at investigating light meson production in light ion collisions and eta meson rare decays at the CELSIUS storage ring in Uppsala is presented. A unique feature of the system is the use of hydrogen pellets as internal targets for the first time. A detailed description of the design, together with the anticipated and achieved performance parameters are given. (C) 2008 Elsevier B.V. All rights reserved.
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| 13. |
- Baussan, E., et al.
(författare)
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A very intense neutrino super beam experiment for leptonic CP violation discovery based on the European spallation source linac
- 2014
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213 .- 1873-1562. ; 885, s. 127-149
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Tidskriftsartikel (refereegranskat)abstract
- Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spoliation Source currently under construction in Lund, Sweden, to deliver, in parallel with the spoliation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spoliation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few mu s with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 sigma significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 sigma if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented.
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| 14. |
- Berlowski, M., et al.
(författare)
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Measurement of eta meson decays into lepton-antilepton pairs
- 2008
-
Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 77:3, s. 032004-
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Tidskriftsartikel (refereegranskat)abstract
- A search for rare lepton decays of the eta meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay eta -> e(+)e(-)e(+)e(-) events are reported with a background of 1.3 +/- 0.2 events. This allows to set an upper limit to the branching ratio of 9.7x10(-5) (90% CL). The branching ratio for the decay eta -> e(+)e(-)gamma is determined to (7.8 +/- 0.5(stat)+/- 0.8(syst))x10(-3) in agreement with world average value. An upper limit (90% CL) for the branching ratio for the eta -> e(+)e(-) decay is 2.7x10(-5) and a limit for the sum of the eta ->mu(+)mu(-)mu(+)mu(-) and eta ->pi(+)pi(-)mu(+)mu(-) decays is 3.6x10(-4).
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| 15. |
- Calén, H., et al.
(författare)
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Detector setup for a storage ring with an internal target
- 1996
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 379:1, s. 57-75
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Tidskriftsartikel (refereegranskat)abstract
- A detector setup for the cooler storage ring CELSIUS is described. The setup detects particles produced in interactions between the internal beam and a cluster-jet target. Particles emitted in the forward direction are measured by means of arrays of plastic scintillators and proportional counters. Particles, particularly photons, emitted more isotropically are measured by means of two calorimeters containing CsI(Na) crystals. The performance of the setup is given for neutral meson production in proton-proton and proton-deuteron interactions in the energy range 290-1360 MeV.
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| 16. |
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| 17. |
- Darve, C., et al.
(författare)
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The superconducting radio-frequency linear accelerator components for the European spallation source : First test results
- 2016
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Ingår i: Proceedings of the 28th Linear Accelerator Conference, LINAC 2016. - 9783954501694 ; , s. 651-656
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Konferensbidrag (refereegranskat)abstract
- The European Spallation Source requires a pulsed linac with an average beam power on the target of 5 MW, which is about five times higher than the most powerful spallation source in operation today. Over 97 % of the acceleration occurs in superconducting cavities. ESS will be the first accelerator to employ double spoke cavities to accelerate beam. Accelerating gradients of 9 MV/meter is required in the spoke section. The spoke section will be followed by 36 elliptical 704 MHz cavities with a geometrical E of 0.67 and elliptical 704 MHz cavities with a geometrical E of 0.86. Accelerating gradients of 16.7 and 20 MV/m are required in the medium and high-E elliptical cavities, respectively. Initial gradient test results will be presented in which results exceed expected requirements.
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| 18. |
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| 19. |
- Keleta, S, et al.
(författare)
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Exclusive measurement of two-pion production in the dd -> He-4 pi pi reaction
- 2009
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 825:1-2, s. 71-90
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Tidskriftsartikel (refereegranskat)abstract
- The results from the first kinematically complete measurement of the dd -> He-4 pi pi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pi pi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV. with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pi pi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, Our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN -> d pi sub-processes. (C) 2009 Elsevier B.V. All rights reserved.
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| 20. |
- Kren, F., et al.
(författare)
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Exclusive measurements of pp -> d pi(+)pi(0) : Double-pionic fusion without ABC effect
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 684:2-3, s. 110-113
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Tidskriftsartikel (refereegranskat)abstract
- Exclusive measurements of the reaction pp -> d pi(+)pi(0) have been carried out at T-p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi(+)pi(0) channel exhibits no enhancement at low invariant pi pi masses, i.e. no ABC effect. Therefore this most basic isovector double-pionic fusion reaction qualifies as an ideal test case for the conventional t-channel Delta Delta excitation process. Indeed, the obtained differential distributions reveal the conventional t-channel Delta Delta mechanism as the appropriate reaction process, which also accounts for the observed energy dependence of the total cross section.
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| 21. |
- Lindroos, Mats, et al.
(författare)
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The European Spallation Source
- 2011
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 269:24, s. 3258-3260
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Tidskriftsartikel (refereegranskat)abstract
- In 2003 the joint European effort to design a European Spallation Source (ESS) resulted in a set of reports, and in May 2009 Lund was agreed to be the ESS site. The ESS Scandinavia office has since then worked on setting all the necessary legal and organizational matters in place so that the Design Update and construction can be started in January 2011, in collaboration with European partners. The Design Update phase is expected to end in 2012, to be followed by a construction phase, with first neutrons expected in 2018-2019. (C) 2011 Elsevier By. All rights reserved.
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| 22. |
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| 23. |
- Schönning, Karin, et al.
(författare)
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Polarisation of the omega meson in the pd -> He-3 omega reaction at 1360 and 1450 MeV
- 2008
-
Ingår i: Physics Letters B. - elsevier : Elsevier BV. - 0370-2693 .- 1873-2445. ; 668:4, s. 258-262
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Tidskriftsartikel (refereegranskat)abstract
- The tensor polarisation of omega mesons produced in the pd -> He-3 omega reaction has been studied at two energies near threshold. The 3 He nuclei were detected in coincidence with the pi(0)pi(+)pi(-) or pi(0)gamma decay products of the omega. in contrast to the case of phi-meson production, the omega mesons are found to be unpolarised. This brings into question the applicability of the Okubo-Zweig-lizuka rule when comparing the production of vector mesons in low energy hadronic reactions.
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| 24. |
- Schönning, Karin, et al.
(författare)
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Production of the omega meson in the pd -> He-3 omega reaction at 1450 MeV and 1360 MeV
- 2009
-
Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 79:4, s. 044002-
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Tidskriftsartikel (refereegranskat)abstract
- The production of omega mesons in the pd -> He-3 omega reaction has been studied at two energies near the kinematic threshold, T-p = 1450 MeV and T-p = 1360 MeV. The differential cross section was measured as a function of the omega c.m. angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections.
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| 25. |
- Skorodko, T., et al.
(författare)
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Exclusive measurement of the pp -> nn pi(+)pi(+) reaction at 1.1 GeV
- 2011
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 47:9, s. 108-
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Tidskriftsartikel (refereegranskat)abstract
- First exclusive data for the pp -> nnp(+)pi(+) reaction have been obtained at CELSIUS with the WASA detector setup at a beam energy of T(p) - 1.1 GeV. Total and differential cross-sections disagree with theoretical calculations, which predict the Delta Delta excitation to be the dominant process at this beam energy. Instead, the data require the excitation of one of the nucleons to a higher-lying Delta state, preferably the Delta(1600)P(33), to be the leading process.
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