| 1. |
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| 2. |
- Paschke, K. D., et al.
(författare)
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Experimental determination of the complete spin structure for (p)over-barp ->(Lambda)over-bar Lambda at p((p)over-bar)=1.637 GeV/c
- 2006
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 74:1, s. 015206-
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Tidskriftsartikel (refereegranskat)abstract
- The reaction (p) over barp -> (Lambda) over bar Lambda -> (p) over bar pi(+)p pi(-) has been measured with high statistics at a beam momentum of p((p) over bar)=1.637GeV/c. The use of a transversely polarized frozen-spin target combined with the self-analyzing property of Lambda/(Lambda) over bar decay allows access to unprecedented information on the spin structure of the interaction. The most general spin-scattering matrix can be written in terms of 11 real parameters for each bin of scattering angle; each of these parameters is determined with reasonable precision. From these results, all conceivable spin correlations are determined with inherent self-consistency. Good agreement is found with the few previously existing measurements of spin observables in (p) over barp ->(Lambda) over bar Lambda near this energy. Existing theoretical models do not give good predictions for those spin observables that had not been previously measured.
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| 3. |
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| 4. |
- Johansson, Tord, et al.
(författare)
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Results from PS185.
- 1999
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Ingår i: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. ; , s. 173C-178C
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Konferensbidrag (refereegranskat)abstract
- The PS185 experiment at LEAR/CERN has studied strangeness production in antiproton-proton collisions. Exclusive final states of antihyperon-hyperon pairs have been measured in order to investigate strange-quark production dynamics. A comprehensive data se
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| 5. |
- Ahrens, J, et al.
(författare)
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First measurement of the helicity-dependent (gamma)over-right-arrow(p)over-right-arrow -> p eta differential cross-section
- 2003
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 17:2, s. 241-244
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Tidskriftsartikel (refereegranskat)abstract
- The helicity dependence of the (γ) over right arrow(p) over right arrow -+ peta reaction has been measured for the first time at a center-of-mass angle theta(eta)*= 70degrees in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam. and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.
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| 6. |
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| 7. |
- Ahrens, J, et al.
(författare)
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Helicity dependence of the (gamma)over-right-arrow (p)over-right-arrow -> n pi(+) pi(0) reaction in the second resonance region
- 2003
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 551:1-2, s. 49-55
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Tidskriftsartikel (refereegranskat)abstract
- The helicity dependence of the total cross section for the (γ) over right arrow(p) over right arrownpi(+) pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV The measurement was performed with the large acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, due to the intermediate production of the D-13 resonance. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 8. |
- Ahrens, J, et al.
(författare)
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Helicity dependence of the gamma p -> N pi channels and multipole analysis in the Delta region
- 2004
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 21:2, s. 323-333
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Tidskriftsartikel (refereegranskat)abstract
- A high-quality double-polarization data set for the helicity dependence of the total and differential cross-sections for both gammap --> Npi channels in the Delta region has been obtained in the framework of the GDH experiment. The experiment, performed at the Mainz microtron MAMI, used a 4pi detection system, a circularly polarized photon beam, and a longitudinally polarized frozen-spin target. These data are included in the database to perform a multipole analysis to determine the properties of the Delta(1232)-resonance. For the resonant Delta(1232) multipoles we find a very good agreement with previous analyses, while the nonresonant ones show significant deviations.
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| 9. |
- Ahrens, J, et al.
(författare)
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Intermediate resonance excitation in the gamma p -> p pi(0)pi(0) reaction
- 2005
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 624:3-4, s. 173-180
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Tidskriftsartikel (refereegranskat)abstract
- The helicity dependence of the total cross section for the (gamma) over right arrow(p) over right arrow -> p pi(0)pi(0) reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement, performed at the tagged photon beam facility of the MAMI accelerator in Mainz, used the large acceptance detector DAPHNE and a longitudinally polarized frozen-spin target. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, most likely due to the intermediate production of the D-13(1520) resonance. However, the contribution of the antiparallel spin configuration, arising from other reaction mechanisms, is also not negligible. This result gives important new information to resolve the existing model discrepancies in the identification of the nucleon resonances contributing to this channel.
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| 10. |
- Dutz, H, et al.
(författare)
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Experimental check of the Gerasimov-Drell-Hearn sum rule for H-1
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:3
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Tidskriftsartikel (refereegranskat)abstract
- For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] mub with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.
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| 11. |
- Dutz, H, et al.
(författare)
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First measurement of the Gerasimov-Drell-Hearn sum rule for H-1 from 0.7 to 1.8 GeV at ELSA
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:19: 192001
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Tidskriftsartikel (refereegranskat)abstract
- To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] mub.
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| 12. |
- Dutz, H, et al.
(författare)
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Measurement of helicity-dependent photoabsorption cross sections on the neutron from 815 to 1825 MeV
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4 pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat)+/- 4.5(syst)] mu b is extracted.
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| 13. |
- Adeva, B, et al.
(författare)
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Measurement of proton and nitrogen polarization in ammonia and a test of equal spin temperature
- 1998
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Ingår i: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT. - : ELSEVIER SCIENCE BV. - 0168-9002. ; 419:1, s. 60-82
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The 1996 data taking of the SMC experiment used polarized protons to measure the spin-dependent structure function g(1) of the proton. Three liters of solid granular ammonia were irradiated at the Bonn electron linac in order to create the paramagnetic ra
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| 14. |
- Winder, Monika, et al.
(författare)
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Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions
- 2017
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 62:4, s. 1541-1551
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications.
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