| 11. |
- 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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| 12. |
- 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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| 13. |
- Bashkanov, M., et al.
(författare)
-
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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| 14. |
- Bashkanov, M., et al.
(författare)
-
Measurement of the slope parameter for the η → 3π0 decay in the pp → ppη reaction
- 2007
-
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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| 15. |
- Bashkanov, M., et al.
(författare)
-
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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| 16. |
- Berlowski, M., et al.
(författare)
-
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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| 17. |
- Brodowski, W, et al.
(författare)
-
Exclusive measurement of pp -> pp pi(+)pi(-) at CELSIUS
- 2000
-
Ingår i: ACTA PHYSICA POLONICA B. - : ACTA PHYSICA POLONICA B, JAGELLONIAN UNIV, INST PHYSICS. - 0587-4254. ; 31:10-11, s. 2295-2298
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Tidskriftsartikel (refereegranskat)abstract
- With the PROMICE/WASA detector setup at CELSIUS the reaction pp --> NN pi pi has been measured in the energy range from 650 to 775 MeV. These data constitute the first exclusive high-statistics measurements on a pure hydrogen target, supplying both differ
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| 18. |
- Calén, H., et al.
(författare)
-
The pp → ppη reaction near the kinematical threshold
- 1996
-
Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 366:1-4, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.
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| 19. |
- Calen, H, et al.
(författare)
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Threshold structure of the quasifree p+n -> d+eta reaction
- 1998
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Ingår i: PHYSICAL REVIEW LETTERS. - : AMERICAN PHYSICAL SOC. - 0031-9007. ; 80:10, s. 2069-2072
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Tidskriftsartikel (refereegranskat)abstract
- The quasifree p + n --> d + eta reaction cross section has been measured at the threshold using 1295 MeV protons in the CELSIUS storage ring and an internal cluster-jet deuterium target. The kinematics is chosen such that the target proton can be assumed
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| 20. |
- Greiff, J, et al.
(författare)
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Pion production in dp -> dN pi reactions with deuteron projectiles - art. no. 064002
- 2000
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Ingår i: PHYSICAL REVIEW C. - : AMERICAN PHYSICAL SOC. - 0556-2813. ; 6206:6, s. 4002-
-
Tidskriftsartikel (refereegranskat)abstract
- Kinematically complete events have been studied for the reactions dp-->dp pi (0) and dp-->dn pi (+) at projectile energies between 437 and 559 MeV. The measurement covers a range of pion momenta eta =p(pi ,c.m.)(max)/m(pi)c from near the production thresh
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