| 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. |
- Artedi, Peter, et al.
(författare)
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Ichthyologia
- 2022
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Bok (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Bargholtz, Chr., et al.
(författare)
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Measurement of the eta -> pi(+)pi(-)e(+)e(-) decay branching ratio
- 2007
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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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| 4. |
- 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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| 5. |
- Bashkanov, M., et al.
(författare)
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Double-Pionic Fusion of Nuclear Systems and the "ABC" Effect : Approaching a Puzzle by Exclusive and Kinematically Complete Measurements
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 052301-
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Tidskriftsartikel (refereegranskat)abstract
- The ABC effect-a puzzling low-mass enhancement in the pi pi invariant mass spectrum, first observed by Abashian, Booth, and Crowe-is well known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on the first exclusive and kinematically complete measurements of the most basic double-pionic fusion reaction pn -> d pi(0)pi(0) at beam energies of 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a (pi pi)(I=L=0) channel phenomenon associated with both a resonancelike energy dependence in the integral cross section and the formation of a Delta Delta system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.
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| 6. |
- Bashkanov, M., et al.
(författare)
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Exclusive measurements of pd -> He-3 pi pi : The ABC effect revisited
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 637:4-5, s. 223-228
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Tidskriftsartikel (refereegranskat)abstract
- Exclusive measurements of the reactions pd -> He-3 pi(+)7 pi(-) and pd -> He-3 pi(0)pi(0) have been carried out at T-p = 0.893 GeV at the CELSIUS storage ring using the WASA detector. The pi(+)pi(-) channel evidences a pronounced enhancement at low invariant pi pi masses-as anticipated from previous inclusive measurements of the ABC effect. This enhancement is seen to be even much larger in the isoscalar pi(0)pi(0) channel. The differential distributions prove this enhancement to be of scalar-isoscalar nature. Delta Delta calculations give a good description of the data, if a boundstate condition is imposed for the intermediate Delta Delta system.
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| 7. |
- Bashkanov, M., et al.
(författare)
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Low-mass pi pi enhancement in baryonic pi pi production : ABC effect revised by exclusive measurements
- 2007
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 22:2-3, s. 625-628
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Tidskriftsartikel (refereegranskat)abstract
- The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance.
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| 8. |
- Bashkanov, M., et al.
(författare)
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Measurement of the slope parameter for the η → 3π0 decay in the pp → ppη reaction
- 2007
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 76:4, s. 048201-
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Bashkanov, M., et al.
(författare)
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Two-pion production in proton-proton collisions
- 2004
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Ingår i: Hadron Spectroscopy, Tenth International Conference on Hadron Spectrscopy, Aschaffenburg, Germany 31 August - 6 September 2003. - 0735401977 ; , s. 241-244
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
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| 11. |
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| 12. |
- Berlowski, M., et al.
(författare)
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Measurement of eta meson decays into lepton-antilepton pairs
- 2008
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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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| 13. |
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| 15. |
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| 16. |
- Britz, Ralf, et al.
(författare)
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Dario tigris and Dario melanogrammus, two new species of miniature chameleon fishes from northern Myanmar (Teleostei: Badidae)
- 2022
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Ingår i: Zootaxa. - : Magnolia Press. - 1175-5326 .- 1175-5334. ; 5138:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Dario tigris, new species, is described from mountain streams south of Mogaung, in the Ayeyarwaddy River basin, Myanmar. It differs from congeneric species by its unique colour pattern, which consists of a series of eight straight vertical bars, the first two of which in males are ash-grey and the subsequent six are orange-red in life, combined with a series of small black spots arranged in three to four rows dorsolaterally on the head and nape. It differs further from its close relative Dario hysginon, with which it may occur syntopically, by fewer dorsal-fin spines (modally 14 vs modally 15), and fewer vertebrae (modally 12+12=24 vs modally 12+13= 25). Dario melanogrammus, new species, is another barred Dario from the Chindwin River basin. It differs from all other species of the genus by its zigzagging dark vertical bars; amongst Myanmar species, it can be further distinguished from D. hysginon and D. tigris by more vertebrae (modally 26 vs 25 in D. hysginon, and 24 in D. tigris).
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| 17. |
- Britzke, Ricardo, et al.
(författare)
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Apistogramma ortegai (Teleostei: Cichlidae), a new species of cichlid fish from the Ampyiacu River in the Peruvian Amazon basin
- 2014
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Ingår i: Zootaxa. - : Magnolia Press. - 1175-5326 .- 1175-5334. ; 3869:4, s. 409-419
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Tidskriftsartikel (refereegranskat)abstract
- Apistogramma ortegai, new species, is described from small streams tributaries of the Ampiyacu River near Pebas, in easternPeru. It belongs to the Apistogramma regani species group and is distinguished from all other species of Apistogrammaby the combination of contiguous caudal spot to bar 7, presence of abdominal stripes, short dorsal-fin lappets in both sexes,absence of vertical stripes on the caudal fin, and reduced number of predorsal and prepelvic scales.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Brodowski, W, et al.
(författare)
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Two-Pion Production in Nucleon-Nucleon Collisions
- 2002
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Ingår i: Proc. Int. Conf. on Production, Properties and Interaction of Mesons, MESON 2002, Cracow, Poland, 2002..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 22. |
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| 23. |
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| 24. |
- Calén, Hans, et al.
(författare)
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Measurement of η meson decays into lepton-antilepton pairs
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A search for rare lepton decays of the η meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay η→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 9.7×10−5 η(90% CL). The branching ratio for the decay η→e+e−γ is determined to (7.8±0.5stat ±0.8syst)×10−3 in agreement with world average value. An upper limit (90% CL) for the branching ratio for the η→e+e− decay is 2.7 × 10−5 and a limit for the sum of the η→μ+μ−μ+μ− and η→π+π−μ+μ− decays is 3.6 × 10−4.
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| 25. |
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