| 1. |
- Ablikim, M., et al.
(author)
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Measurements of (XcJ)-> K+K-K+K- decays
- 2006
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:3, s. 197-202
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Journal article (peer-reviewed)abstract
- Using 14M psi(2S) events taken with the BESII detector, chi(cJ) -> 2(K+K-) decays are studied. For the four-kaon final state, the branching fractions are B(chi(c0,1,2) ->.2(K+K-)) = (3.48 +/- 0.23 +/- 0.47) x 10(-3), (0.70 +/- 0.13 +/- 0.10) x 10(-3), and (2.17 +/- 0.20 +/- 0.31) x 10(-3). For the phi K+K- final state, the branching fractions, which are measured for the first time, are B(chi(c0,1,2) -> phi K+K-) = (1.03 +/- 0.22 +/- 0.15) x 10(-3), (0.46 +/- 0.16 +/- 0.06) x 10(-3), and (1.67 +/- 0.26 +/- 0.24) x 10(-4). For the phi phi final state, B(chi(c0,2) -> phi phi) = (0.94 +/- 0.21 +/- 0.13) x 10(-3) and (1.70 +/- 0.30 +/- 0.25) x 10(-3).
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| 2. |
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| 3. |
- Bargholtz, Chr., et al.
(author)
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The WASA detector facility at CELSIUS
- 2008
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 594:3, s. 339-350
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Journal article (peer-reviewed)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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| 4. |
- Bashkanov, M., et al.
(author)
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Measurement of the slope parameter for the η → 3π0 decay in the pp → ppη reaction
- 2007
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In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 76:4, s. 048201-
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Journal article (peer-reviewed)abstract
- The CELSIUS-WASA setup is used to measure the 3π0 decay of η mesons produced in pp interactions with beam kinetic energies of 1.36 and 1.45 GeV. The efficiency-corrected Dalitz plot and density distributions for this decay are shown, together with a fit of the quadratic slope parameter α yielding α = −0.026 ± 0.010(stat) ± 0.010(syst). This value is compared to recent experimental results and theoretical predictions.
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| 5. |
- Bashkanov, M., et al.
(author)
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Two-pion production in proton-proton collisions
- 2004
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In: Hadron Spectroscopy, Tenth International Conference on Hadron Spectrscopy, Aschaffenburg, Germany 31 August - 6 September 2003. - 0735401977 ; , s. 241-244
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Conference paper (other academic/artistic)
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Lehmann, I., et al.
(author)
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Vacuum predictions and measurements for an internal Pellet Target at a storage ring
- 2008
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In: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 82:6, s. 645-650
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Journal article (peer-reviewed)abstract
- Measurements with low Z targets at internal experiments typically imply a gas load which deteriorates the vacuum of a storage ring. Future experiments need reliable estimates for the expected vacuum conditions in order to design 4π detectors closely surrounding the interaction area. We present a method for the calculation of the resulting vacuum of such a complex system using a Pellet Target. In order to test the method, a vacuum system with diagnostic tools has been set-up and a Pellet Target was operated under realistic conditions. The results for the absolute vacuum agree within factors of two with the expected pressures.
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| 10. |
- Lundborg, Agnes, et al.
(author)
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Charmonium in production in ppbar annihilation: Estimating cross sections from decay widths
- 2005
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In: arXiv: Electronical access to physics preprints. ; hep-ph:0507166
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Journal article (other academic/artistic)abstract
- The cross sections for the charmonium production processes p+pbar->m+psi, where m is a light meson and psi is a charmonium state, are of great interest for the planned p+pbar experiment PANDA. In this paper we estimate these cross sections using known results for the decays psi->m+p+pbar, which are related to these reactions by crossing. In lieu of detailed experimental data on the decay Dalitz plots, we assume a constant amplitude as a first approximation; this implies a simple relation between the cross sections and decay widths. The single measured exclusive cross section of this type is p+pbar->pi0+Jpsi, which was reported by E760 to be 130+-25 pb near sqrt(s)=3.5-3.6 GeV. In comparison, our constant amplitude estimate is about 300 pb at this energy. This suggests that our approach is useful as a simple estimate, but should be refined through detailed modeling of resonances and other energy-dependent effects in the experimental psi->m+p+pbar Dalitz plots.
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| 11. |
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| 12. |
- Lundborg, Agnes, 1977-
(author)
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The Charm of Excited Glue : Charmonium in e+e– and ppbar collisions
- 2007
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Doctoral thesis (other academic/artistic)abstract
- This thesis treats the mass range of charmonium states and excited gluonic fields in two experiments, BESII and PANDA, and outlines a phenomenological model that connects them.In BESII, e+e– form a charmonium initial state, which is utilised as a source for secondary particles. The analysed channels, ψ´→ γK+K– and ψ´→ γπ+π–, give access to intermediate scalar states such as the two glueball candidates: f0(1500) and f0(1710). The f0(1710) is indeed observed in decay into both π+π– and K+K– and the f0(1500) is accepted as a necessary part of the π+π– signal at the moderate 5% level. In addition, we observe the two tensor states f2(1270) (in both channels) and f2´(1525) (in K+K–), but the need for the f2´(1525) is not firmly established. The region around 2 GeV/c2 is fitted with an f4(2050) and an f0(2200) in π+π–. This region is fairly flat in K+K– with a slight peak at the f0(2200). Branching ratios for all eight channels are given. A fit to the angular distribution of ψ´→ γ f2(1270) → γ π+π–gave two possible solutions for the relative importance of helicity projections zero, one and two.The future ppbar experiment PANDA is still in the development phase; important physics goals have been defined and we are now taking on the laborious task of constructing a detector that is able to fulfil them. A simulation investigation of a theoretically preferred JPC=1–+ charmonium hybrid (Hc) is presented: ppbar → Hcπ0/η, Hc → χc1 (π0π0)S–wave, χc1 → J/ψπ0, with a final state of seven photons and a lepton pair. To detect this channel next to full coverage of CM phase space is needed and as little material as possible before the electromagnetic calorimeter. A second simulation study of ppbar → ηc → γγ at PANDA, suggests that the channel should be possible to detect with a signal-to-background ratio of 5±1 and a detection efficiency of at least 10%. By assuming a constant matrix element we obtain a relation between the decay width for ψ → ppbar+m, which has been measured at BES for several cases, and the cross section for ppbar charmonium production in association with the same light meson, m (at for example PANDA). Cross sections of ~300–3000 pb were predicted for J/ψ production and ~30 pb for ψ' production. Isoscalars seem to be preferred to isovectors in J/ψ production, this might however be an artefact of simplifications within the model. A comparison with the only measured cross section, ppbar → J/ψπ0, suggests that the model is useful as a first estimate.
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| 13. |
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| 14. |
- Nordhage, Örjan, 1978-
(author)
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On a Hydrogen Pellet Target for Antiproton Physics with PANDA
- 2006
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Doctoral thesis (other academic/artistic)abstract
- The PANDA experiment is a part of the future FAIR accelerator facility and will study the strong interaction by detecting the reaction products from antiproton-proton annihilations in a near full solid-angle configuration. One option for the internal proton target in PANDA is frozen micro-spheres of hydrogen, so-called pellets.Such a pellet target is interesting because of the unique characteristics it offers; the high target thickness, the small interaction volume, the minimal gas load on the vacuum system, and the possibility of tracking individual pellets. Nevertheless, it is possible to allocate the bulky equipment needed to produce the pellets at a few meters away from the beam. This way particle detectors can be located close and almost fully around the interaction point.This thesis is devoted to the optimization of a pellet target. To perform measurements, a Pellet-Test Station was built at The Svedberg Laboratory, Uppsala. For the first time, experimental results show the pellet distribution in space and time, and in addition, the vacuum along the pellet pipes. Furthermore, dedicated measurements carried out at CELSIUS/WASA demonstrate the existence of pellet heating as a result of beam-target interactions.In performing calculations, the potential problems with pellet heating at PANDA are outlined. Moreover, to look at the consequences for the desired physics, a reaction involving short-lived D-mesons has been used to show the advantages of pellets compared to a more spacious target.In conclusion, these studies lead to a deeper understanding of the pellet properties, which makes it possible to suggest future improvements, such as cooling with no vibrations.
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| 15. |
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| 16. |
- Nordhage, Örjan, et al.
(author)
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Tracked pellets - a way to improve the efficiency of charmonium studies
- 2006
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 568:2, s. 561-565
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Journal article (peer-reviewed)abstract
- We investigate the possibility of tracking individual hydrogen micro-spheres from an internal pellet target. Such a method aims to provide the primary vertex of a reaction to within about 100 mu m, without utilizing any detector response. Apart from background considerations the knowledge of the reaction vertex may be essential for the reconstruction of many physics channels. This is in particular true for the study of the Psi(3770) decay into D-mesons planned at the PANDA detector at the future FAIR facility. Here, the reconstruction of displaced vertices is especially difficult since neutral particles are involved.Studies with a pellet target at The Svedberg Laboratory, Uppsala, show the technical feasibility of a tracking system utilizing fast CCD line-scan cameras. Simulations for the reaction pp -> Psi(3770) -> D+D- prove the large impact such a system would have on the data taking and reconstruction at PANDA.
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| 17. |
- Pauly, C., et al.
(author)
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The pp→ppπππ reaction channels in the threshold region
- 2007
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 649:2-3, s. 122-127
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Journal article (peer-reviewed)abstract
- The cross section for direct neutral and charged three pion production in pp interactions was measured at excess energies in the range 160–216 MeV. That comprises the first measurement of the pp→ppπ0π0π0 reaction and the direct comparison with the pp→ppπ+π−π0 process. The experiment was performed above the η meson production threshold and the cross section could be directly normalized to the cross section of the pp→ppη reaction, with the η decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio σ(pp→ppπ+π−π0)/σ(pp→ppπ0π0π0) is compared to predictions of dominance of different isobars in the intermediate state.
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| 18. |
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| 19. |
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| 20. |
- Wiedner, Ulrich
(author)
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Antiproton Physics at GSI
- 2003
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In: Exotic Atoms - Future Perspectives. - 3700131895
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Conference paper (peer-reviewed)
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| 21. |
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| 22. |
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| 23. |
- Wiedner, Ulrich
(author)
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Hadron Physics with Antiprotons
- 2003
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In: Proc. XVI Particles and Nuclei International Conference, PANIC02, Osaka, Japan, 2002, Nucl. Phys.. ; , s. 601c-604c
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Conference paper (peer-reviewed)
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| 24. |
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