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Sökning: WFRF:(Zabierowski S)

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1.
  • Forrest, ARR, et al. (författare)
  • A promoter-level mammalian expression atlas
  • 2014
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 507:7493, s. 462-
  • Tidskriftsartikel (refereegranskat)
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2.
  • Adlarson, Patrik, et al. (författare)
  • Search for the eta mesic He-3 in the pd -> dp pi(0) reaction with the WASA-at-COSY facility
  • 2020
  • Ingår i: Physical Review C. Nuclear Physics. - : AMER PHYSICAL SOC. - 0556-2813 .- 1089-490X. ; 102:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The excitation function for the pd -> dp pi(0) reaction has been measured byWASA-at-COSY experiment with the aim of searching for He-3-h mesic nuclei. The measurement in the vicinity of h meson production was performed using a ramped proton beam. The data analysis and interpretation was carried out with the assumption that the h mesic helium decays via the formation of an intermediate N*(1535) resonance. No direct signal of the. mesic nucleus is observed in the excitation function. We determine a new improved upper limit for the total cross section for the bound state production and decay in the pd -> (He-3-eta)(bound) -> dp pi(0) process. It varies between 13 nb to 24 nb for the bound state with width in the range Gamma is an element of ( 5, 50) MeV.
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3.
  • Adlarson, Patrik, et al. (författare)
  • Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
  • 2011
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
  • 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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4.
  • Adlarson, Patrik, et al. (författare)
  • Abashian-Booth-Crowe resonance structure in the double pionic fusion to He-4
  • 2012
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 86:3, s. 032201-
  • Tidskriftsartikel (refereegranskat)abstract
    • Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction dd -> He-4 pi(0)pi(0) have been performed in the energy range 0.8-1.4 GeV covering thus the region of the Abashian-Booth-Crowe effect, which denotes a pronounced low-mass enhancement in the pi pi invariant mass spectrum. The experiments were carried out with the WASA detector setup at the cooler synchrotron at Forshungszentrum Julich GmbH. Similar to the observation in the basic pn -> d pi(0)pi(0) reaction, the data reveal a correlation between the ABC effect and a resonancelike energy dependence in the total cross section. The maximum occurs at m = 2.37 GeV + 2m(N), i.e., at the same position as in the basic reaction. The observed resonance width Gamma approximate to 160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a pn resonance formation during the reaction process.
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5.
  • Adlarson, Patrik, et al. (författare)
  • Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
  • 2012
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
  • 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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6.
  • Adlarson, P., et al. (författare)
  • Isospin decomposition of the basic double-pionic fusion in the region of the ABC effect
  • 2013
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 721:4-5, s. 229-236
  • Tidskriftsartikel (refereegranskat)abstract
    • Exclusive and kinematically complete high-statistics measurements of the basic double-pionic fusion reactions pn -> d pi(0)pi(0), pn -> d pi(+)pi(-) and pp -> d pi(+)pi(0) have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the d pi(0)pi(0) channel exhibits the ABC effect, i.e. a low-mass enhancement in the pi pi-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the d pi(+)pi(0) channel shows a smooth behavior consistent with the conventional t-channel Delta Delta process. The d pi(+)pi(-) data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account.
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7.
  • Adlarson, Patrik, et al. (författare)
  • pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration
  • 2012
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 256-262
  • 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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8.
  • Adlarson, Patrik, et al. (författare)
  • Search for eta-mesic He-4 with the WASA-at-COSY detector
  • 2013
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:3, s. 035204-
  • Tidskriftsartikel (refereegranskat)abstract
    • An exclusive measurement of the excitation function for the dd -> (3)Hep pi(-) reaction was performed at the Cooler Synchrotron COSY-Julich with the WASA-at-COSY detection system. The data were taken during a slow acceleration of the beam from 2.185 to 2.400 GeV/c crossing the kinematic threshold for the eta-meson production in the dd -> He-4 eta reaction at 2.336 GeV/c. The corresponding excess energy with respect to the He-4-eta system varied from -51.4 to 22 MeV. The integrated luminosity in the experiment was determined using the dd -> (3)Hen reaction. The shape of the excitation function for the dd -> (3)Hep pi(-) reaction was examined. No signal of the He-4-eta bound state was observed. An upper limit for the cross section for the bound state formation and decay in the process dd -> (He-4-eta)(bound) -> (3)Hep pi(-) was determined on the 90% confidence level and it varies from 20 to 27 nb for the bound state width ranging from 5 to 35 MeV, respectively. 
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9.
  • Adlarson, Patrik, et al. (författare)
  • Search for η mesic 3He with the WASA-at-COSY facility in the pd -> 3He2γ and pd -> 3He6γ  reaction
  • 2020
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 802
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the experimental search for the bound state of an eta meson and He-3 nucleus performed using the WASA-at-COSY detector setup. In order to search for the eta-mesic nucleus decay, the pd -> (3)He2(gamma) and pd -> (3)He6 gamma channels have been analysed. These reactions manifest the direct decay of the ti meson bound in a He-3 nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to a He-3-eta nucleus width Gamma above 20 MeV and binding energy B-s between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the eta-mesic He-3 nucleus formation followed by the eta meson decay which varies between 2 nb and 15 nb depending on possible bound state parameters.
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10.
  • Adlarson, Patrik, et al. (författare)
  • Spin Dependence of eta Meson Production in Proton-Proton Collisions Close to Threshold
  • 2018
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 120:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high polarization degree of the proton beam of COSY, the reaction →pp→ppη has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than 1 order of magnitude with respect to previous results, allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q=15  MeV, signaling s-wave production with no evidence for higher partial waves. At Q=72  MeV the data reveal strong interference of Ps and Pp partial waves and cancellation of (Pp)2 and Ss∗Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the η meson.
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  • Resultat 1-10 av 57

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