| 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. |
- Adlarson, Patrik, et al.
(författare)
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Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
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Tidskriftsartikel (refereegranskat)abstract
- An exclusive measurement of the decay eta -> pi(+) pi(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction pd -> He-3 X at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on 13 960 +/- 140 events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta -> pi(+) pi(-) gamma. A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi(+) pi(-) system.
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| 3. |
- Adlarson, Patrik, et al.
(författare)
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pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 256-262
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Tidskriftsartikel (refereegranskat)abstract
- The reaction pp -> pp pi(0)pi(0) has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +/- 21(systematic) +/- 58(normalization)) mu b. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found.
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| 4. |
- Akram, Adeel
(författare)
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Towards a realistic hyperon reconstruction with PANDA at FAIR
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The goal of the PANDA (anti-Proton ANnihilation at DArmstadt) experiment at FAIR (Facility for Anti-proton and Ion Research) is to study strong interactions in the confinement domain. In PANDA, a continuous beam of anti-protons () will impinge on a fixed hydrogen (p) target inside the High Energy Storage Ring (HESR), a feature intended to attain high interaction rates for various physics studies e.g. hyperon production. Two types of hydrogen targets are under development: a pellet target and a cluster-jet target where either high-density pellets or clusters of cooled hydrogen gas will be injected at the interaction point. The residual gas from the target system is expected to dissipate along the beam pipe resulting in a target that is effectively extended outside the designed interaction point. The realistic density profile of target and residual gas has implications for physics studies, e.g. in the ability to select signals of interest and, at the same time, suppress background. All hyperon simulations in PANDA until now have been performed under ideal conditions. In this work, I will for the first time implement more realistic conditions for the beam-target interaction and carry out simulations using the as benchmark channel. The impact of the different configurations of the vacuum system will be discussed in detail.In addition, I will present tests of some of the PANDA's particle track finders that are not based on ideal pattern recognition approaches. The results will provide important guidance for future tracking developments within PANDA.
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| 5. |
- Andersson Sundén, Erik, et al.
(författare)
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Citizen Science and Radioactivity
- 2019
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Ingår i: Nuclear Physics News. - : Informa UK Limited. - 1050-6896 .- 1061-9127 .- 1931-7336. ; 29:2, s. 25-28
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 6. |
- Archilli, F., et al.
(författare)
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Search for a vector gauge boson in phi meson decays with the KLOE detector KLOE-2 Collaboration
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 251-255
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Tidskriftsartikel (refereegranskat)abstract
- The existence of a light dark force mediator has been tested with the KLOE detector at DA Phi NE. This particle, called U. is searched for using the decay chain phi -> eta U, eta -> pi(+)pi(-)pi(0), U -> e(+)e(-). No evidence is found in 1.5 fb(-1) of data. The resulting exclusion plot covers the mass range 5 < M-U < 470 MeV, setting an upper limit on the ratio between the U boson coupling constant and the One structure constant, alpha'/alpha, of <= 2 x 10(-5) at 90% C.L. for 50 < M-U < 420 MeV.
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| 7. |
- Babusci, D., et al.
(författare)
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A new limit on the CP violating decay K-S -> 3 pi(0) with the KLOE experiment
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 723:1-3, s. 54-60
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Tidskriftsartikel (refereegranskat)abstract
- We have carried out a new direct search for the CP violating decay K-S -> 3 pi(0) with 1.7 fb(-1) of e(+)e(-) collisions collected by the KLOE detector at the Phi-factory DA Phi NE. We have searched for this decay in a sample of about 5.9 x 10(8) KSKL events tagging the K-S by means of the K-L interaction in the calorimeter and requiring six prompt photons. With respect to our previous search, the analysis has been improved by increasing of a factor four the tagged sample and by a more effective background rejection of fake K-S tags and spurious clusters. We find no candidates in data and simulated background samples, while we expect 0.12 standard model events. Normalizing to the number of K-S -> 2 pi(0) events in the same sample, we set the upper limit on BR(K-S -> 3 pi(0)) <= 2.6 x 10(-8) at 90% C.L., five times lower than the previous limit. We also set the upper limit on the eta(000) parameter, vertical bar eta(000)vertical bar <= 0.0088 at 90% C.L., improving by a factor two the latest direct measurement. (c) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Babusci, D., et al.
(författare)
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Limit on the production of a light vector gauge boson in phi meson decays with the KLOE detector
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 720:1-3, s. 111-115
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Tidskriftsartikel (refereegranskat)abstract
- We present a new limit on the production of a light dark-force mediator with the KLOE detector at DA Phi NE. This boson, called U, has been searched for in the decay phi -> eta U, U -> e(+)e(-), analyzing the. decay eta -> pi(0)pi(0)pi(0) in a data sample of 1.7 fb(-1). No structures are observed in the e(+)e(-) invariant mass distribution over the background. This search is combined with a previous result obtained from the decay eta -> pi(+)pi(-)pi(0), increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of alpha'/alpha < 1.7 x 10(-5) for 30 < M-U < 400 MeV and alpha'/alpha <= 8 x 10(-6) for the sub-region 50 < M-U <210 MeV. This result assumes the Vector Meson Dominance expectations for the phi eta gamma* transition form factor. The dependence of this limit on the transition form factor has also been studied.
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| 9. |
- Babusci, D., et al.
(författare)
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Measurement of eta meson production in gamma gamma interactions and Gamma(eta -> gamma gamma) with the KLOE detector
- 2013
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :1, s. 119-
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of eta meson production in photon-photon interactions produced by electron-positron beams colliding with root s = 1 GeV. The measurement is done with the KLOE detector at the phi-factory DA Phi NE with an integrated luminosity of 0.24 fb(-1). The e(+)e(-) -> e(+)e(-)eta cross section is measured without detecting the outgoing electron and positron, selecting the decays eta -> pi(+)pi(-)pi(0) and eta -> pi(0)pi(0)pi(0). The most relevant background is due to e(+)e(-) -> eta gamma when the monochromatic photon escapes detection. The cross section for this process is measured as sigma(e(+)e(-) -> eta gamma) = (856 +/- 8(stat) +/- 16(syst)) pb. The combined result for the e(+)e(-) -> e(+)e(-)eta cross section is sigma(e(+)e(-) -> e(+)e(-)eta) = (32.72 +/- 1.27(stat) +/- 0.70(syst)) pb. From this we derive the partial width Gamma(eta -> gamma gamma) = (520 +/- 20(stat) +/- 13(syst)) eV. This is in agreement with the world average and is the most precise measurement to date.
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| 10. |
- Babusci, D., et al.
(författare)
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Measurement of Γ(η→π+π-γ)/Γ(η→π+π-π0) with the KLOE detector
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:3, s. 910-914
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Tidskriftsartikel (refereegranskat)abstract
- The ratio Rη=Γ(η→π+π-γ)/Γ(η→π+π-π0) has been measured by analysing 22 million φ→ηγ decays collected by the KLOE experiment at DAΦNE, corresponding to an integrated luminosity of 558 pb-1. The η→π+π-γ proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη=0.1856±0.0005stat±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π-γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α=(1.32±0.08stat-0.09syst+0.10±0.02theo) GeV-2.
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| 11. |
- Babusci, D., et al.
(författare)
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Precision measurement of sigma (e(+)e(-) -> pi(+)pi(-)gamma)/sigma(e(+)e(-) ->mu(+)mu(-)gamma) and determination of the pi(+)pi(-) contribution to the muon anomaly with the KLOE detector
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 720:4-5, s. 336-343
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the ratio cr (e(+)e(-) -> pi(+)pi(-)gamma)/sigma(e(+)e(-) -> mu(+)mu(-)gamma), with the KLOE detector at DA Phi NE for a total integrated luminosity of similar to 240 pb(-1). From this ratio we obtain the cross section sigma (e(+)e(-) -> pi(+)pi(-)gamma). From the cross section we determine the pion form factor vertical bar F-pi vertical bar(2) and the two-pion contribution to the muon anomaly a(mu) for 0.592< M-pi pi < 0.975 GeV, Delta(pi pi) a(mu) = (385.1 +/- 1.1(stat) +/- 2.7(sys+theo)) x 10(-10). This result confirms the current discrepancy between the Standard Model calculation and the experimental measurement of the muon anomaly. (c) 2013 Elsevier B.V. All rights reserved.
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| 12. |
- Babusci, D., et al.
(författare)
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Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment
- 2014
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 730, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- Neutral kaon pairs produced in phi decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process phi -> KSKL -> pi(+)pi(-)pi(+)pi(-) based on 1.7 fb(-1) of data collected by the KLOE experiment at the Frascati phi-factory DA Phi NE. The data are used to perform a Measurement of the CPT-violating parameters Delta a(mu) for neutral kaons in the context of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are: Delta a(0) = (-6.0 +/- 7.7(stat)+/- 3.1(syst)) X 10(-18) GeV, Delta a(x) = (0.9 +/- 1.5(stat)+/- 0.6(syst)) X 10(-18) GeV, Delta a(y) = (-2.0 +/- 1.5(stat)+/- 0.5(syst)) X 10(-18) GeV, Delta a(z) = (3.1 +/- 1.7(stat)+/- 0.5(syst)) X 10(-18) GeV. These are presently the most precise measurements in the quark sector of the Standard Model Extension. (C) 2014 The Authors. Published by Elsevier B.V.
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| 13. |
- 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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| 14. |
- 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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| 15. |
- 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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| 16. |
- 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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| 17. |
- 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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| 18. |
- 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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| 19. |
- Bashkanov, M., et al.
(författare)
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WHAT IS THE NATURE OF THE ABC EFFECT?
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 627-629
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Tidskriftsartikel (refereegranskat)abstract
- The ABC effect - an intriguing low-mass enhancement in the pi pi invariant mass spectrum - is known from inclusive measurements of two-pion production in nuclear fusion reactions. Exclusive measurements have been carried out at CELSIUS/WASA and WASA-at-COSY for the fusion reactions leading to d, (3)He and (4)He. They all reveal this effect to be of isoscalar nature and associated with a narrow Lorentzian-shaped structure in the total cross section. The latter could point to the formation of an isoscalar resonance, which couples to the pn channel as well as to an intermediate Delta Delta state.
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| 20. |
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| 21. |
- Berlowski, Marcin, et al.
(författare)
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SEARCH FOR EXOTIC EFFECTS IN eta MESON LEPTONIC DECAYS
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 630-631
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Tidskriftsartikel (refereegranskat)abstract
- The search for the decay eta -> e(+)e(-) was carried out using the WASA detector at the COSY storage ring. Data were taken during a two week experimental run in Sept-Nov 2008 in which about 10(7) eta mesons were collected from the reaction of pp -> pp eta at energy of 1.4 GeV. Background studies were performed for several different reactions. The performance of the WASA detector for the measurement of electron-positron pairs based on the single Dalitz decay of the eta meson was studied. We also identified a statistically significant data sample of other more frequent leptonic decays.
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| 22. |
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| 23. |
- Bhattacharyya, Anirban, et al.
(författare)
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ESS RF Source and Spoke Cavity Test Plan
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes the test plan for the first high power RF source, ESS prototype double spoke cavity and ESS prototype cryomodule at the FREIA Laboratory.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- 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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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Farabolini, Wilfrid, et al.
(författare)
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Two Beam Test Stand Experiments in the CTF3 Facility
- 2011
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Konferensbidrag (refereegranskat)abstract
- The CLEX building in the CTF3 facility is the placewhere essential experiments are performed to validate theTwo-Beam Acceleration scheme upon which the CLICproject relies. The Drive Beam enters the CLEX hall afterbeing recombined in the Delay loop and the CombinerRing in intense beam trains of 24 A – 120 MeV lasting140 ns and bunched at 12 GHz, although other beamparameters are also accessible. This beam is thendecelerated in dedicated structures installed in the TestBeam Line (TBL) and in the Two-Beam Test Stand(TBTS) aimed at delivering bursts of 12 GHz RF power.In the TBTS this power is used to generate a highaccelerating gradient of 100 MV/m in specially designedaccelerating structures. To assess the performances ofthese structures a probe beam is used, produced by asecond Linac. We report here various experimentsconducted in the TBTS making use of the versatility ofthe probe beam and of dedicated diagnostics.
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| 35. |
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| 36. |
- Freyhult, Lisa, 1977-, et al.
(författare)
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Working with context rich problems to teach problem solving
- 2017
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Ingår i: Transforming patterns through the scholarship of teaching and learning.
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Konferensbidrag (refereegranskat)abstract
- The ability to solve problems is an important ability for scientists as well as engineers and something we identify as a key competence for our students. Problem solving is often examined but still students complain about the difficulty of the examination, describing the problems as more difficult than the problems they have encountered previously.Our study suggests that our students often use inefficient strategies for problem solving, like pattern matching or trying to find a mathematical formula that fits the situation. It is clear that these strategies will not work and they become less and less useful the further the students get in their education.To train problem solving and to prepare students to handle unknown problems and situations cooperative problem solving and context rich problems have been identified as efficient strategies [1,2]. These methods have specifically been used in early courses in mechanics and similar experiences with open ended but shorter problems have been described in [3,4,5]. We have applied these strategies in a more advanced course in Lagrangian mechanics. Students perceive this topic as somewhat abstract and disconnected from everyday experience and lack a clear relevance to their professional role. We describe our work as a team of teachers and our experience introducing a new methodology in the course with the goal to teach in a way that discourages inefficient problem solving strategies.ReferencesHeller, P och Heller, K (2010) Cooperative Problem Solving in Physics A User’s ManualHeller, P, Keith, R och Andersson (1992), Teaching problem solving through cooperative grouping. Part 1: Group versus individual problem solving, S, Am. J. Phys. 60, 627; Heller, P och Hollabaugh, M (1992), Teaching problem solving through cooperative grouping. Part 2: Designing problems and structuring groups, Am. J. Phys. 60, 637Maloney, D., Research on problem solving in physics, in D. Gabel (ed.) (1994), Handbook of research in science teaching and learning, New YorkWedelin, D., Adawi, T., Jahan T. and Andersson, S., (2015), Investigating and developing engineering students’ mathematical modelling and problem-solving skills, European Journal of Engineering Education, 40:5, pp. 557-572Wedelin, D. och Adawi, D. (2015), Warming up for PBL: a course in mathematical modelling and problem solving for engineering students Högre utbildning Vol. 5, No. 1, pp. 23-34
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| 37. |
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| 38. |
- Föhl, K, et al.
(författare)
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The WASA focussing light guide disc DIRC
- 2012
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 7, s. C01002-
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Tidskriftsartikel (refereegranskat)abstract
- Two Disc DIRC prototypes have been designed and built and are shortly being tested with proton test beams. Different in design details, both aim to provide the WASA-at-COSY experiment with a particle velocity measurement that improves the missing mass resolution. This paper shows the difference in concept between these two designs and also compares to designs that have been proposed for PANDA.
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| 39. |
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| 40. |
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| 41. |
- Hejny, Volker, et al.
(författare)
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CHARGE SYMMETRY BREAKING IN dd -> (4)He pi(0) WITH WASA-at-COSY
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 595-597
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Tidskriftsartikel (refereegranskat)abstract
- Charge symmetry breaking effects can be used as an experimental tool to study quark mass effects. Using recent high precision data from TRIUMF and IUCF an international theory collaboration is working on a consistent description within the framework of chiral pertubation theory. The WASA-at-COSY collaboration has started an experimental program extending the studies on the reaction dd -> (4)He pi(0) towards higher excess energies in order to provide necessary information on the contribution of p-waves. First preliminary results on the total cross section at Q = 60 MeV are presented.
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| 42. |
- Hodana, Malcorzata, et al.
(författare)
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STUDY OF THE eta -> gamma e(+)e(-) DECAY WITH THE WASA-at-COSY
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 650-651
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Tidskriftsartikel (refereegranskat)abstract
- In October 2008, the WASA-at-COSY collected more than 10(7) events for the pd -> (3)He eta reaction. The aim is the determination of the invariant mass of the lepton pairs created in the Dalitz decay eta -> gamma e(+)e(-). The e(+)e(-) invariant mass spectrum is directly related to the distribution of the four-momentum squared of the virtual photon from the eta -> gamma gamma* process and hence it allows for the study of the transition form factor which in turn reflects the structure of the decaying meson.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Jacewicz, Marek
(författare)
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Dark currents studies with the Uppsala X-band Spectrometer at XBox test stand at CERN
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vacuum arcs is the phenomenon which limits the performance of normal conducting acceleratorcavities. It closely depends on electron field emission, which is consider a precursor for the creationof a vacuum discharge. These processes are still not fully understood, but we know that theydepend on the physical properties of the surfaces and bulk materials used in the acceleratorstructures. We need to come at these problems with a multidisciplinary approach, comprisingaccelerator, material and surface physics, for both experimental and theoretical analysis.The field emission current emitted during operation of the RF cavity is typically refer to as thedark current. Behavior of the dark current can give useful information about changes inside thestructure during conditioning and thus into the physics of the vacuum arcs. The Uppsala groupuses a magnetic spectrometer to look at the changes, both spatially on the screen and by measuringthe energy spectrum of the escaping electrons during conditioning of CLIC X-band structuresin dedicated high-power RF test stand at CERN. The spectrometer was originally designedto measure the electrons from the breakdown events with much higher intensities than the darkcurrent signals. In this paper we present the attempt to measure the dark current with the samesetup.
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| 49. |
- Jacewicz, Marek, et al.
(författare)
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Instrumentation for the 12 GHz Stand-alone Test-stand to Test CLIC Acceleration Structures
- 2011
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Konferensbidrag (refereegranskat)abstract
- Vacuum breakdown is one of the primary limitations inthe design and construction of high energy accelerators operating with warm accelerating structures (ACS) such asthe CLIC linear collider because the mechanisms that causethe breakdown are still a mystery. The ongoing experimental work is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the observed discharges. The CLIC collaboration is preparing a dedicated 12 GHz test-stand to validate feasibility of different models of accelerating structures and observe the characteristics of the RF dischargesand their eroding effects on the ACS. The instrumentationfor the test-stand must be versatile and allow for the conditioning of the ACS with measurements of the breakdownrates at different power levels as well as detection of thedark current and light emission directly relevant to breakdown physics. For that purpose we are developing 2 instruments. A pepper-pot chamber with an external magnetic spectrometer for measurement of the spatial and energy distributions of the electrons emitted from the ACSand an optical laser system for probing the ACS to observethe effect of a discharge on the transmitted light
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| 50. |
- Jacewicz, Marek, 1973-
(författare)
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Measurement of the Reaction pp→ppπ+π-π0 with CELSIUS/WASA at 1.36 GeV
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A versatile detector setup prepared by the CELSIUS/WASA collaboration for exclusive studies of rare processes produced in proton and deuteron collisions with hydrogen and deuterium pellet targets is presented. For the near-threshold production of light mesons, π0 and η, the scattered beam and target particles are measured in the forward detector, while the products of the decaying mesons are registered in a central detector covering close-to-4π sr.The central detector is composed of a mini-drift chamber consisting of 1738 straw tubes for tracking of the charged particles and a plastic scintillator barrel consisting of 146 scintillation counters providing fast signals of the passing particles. These two detector parts are placed inside of a superconducting solenoid providing an axial magnetic field.Outside of the solenoid is placed an electromagnetic calorimeter consisting of 1012 CsI crystals. The construction, calibration and performance of the plastic scintillator barrel is presented in detail. Its main purpose is the discrimination of charged and neutral particles on the trigger level. It is also used for the identification of charged particles by ΔE-p (ΔE-E) technique in the off-line analysis.The mini-drift chamber is a detector for determination of particles momenta and reaction vertex. It is built with minimum structural material and designed to withstand high particle fluxes at a luminosity 1032cm-2s-1. The design of the mini-drift chamber, a description of the calibration procedure, its performance and integration in the data analysis are presented.The overall performance of the WASA detector is demonstrated by the analysis of the pp→ppπ+π-π0 reaction at 1.36 GeV incident proton energy. The total cross section for the non-resonant part of the reaction is estimated for the first time in this energy region to be 4.6 ±1.2 -0.9 +0.7 μb. The pp→ppη part of the total reaction cross section is estimated to be 4.8 μb which is consistent with the existing experimental information.
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