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Träfflista för sökning "WFRF:(Foehl K.) "

Search: WFRF:(Foehl K.)

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1.
  • Singh, B. P., et al. (author)
  • Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
  • 2015
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:8
  • Journal article (peer-reviewed)abstract
    • Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.
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2.
  • Erni, W., et al. (author)
  • Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
  • 2013
  • In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
  • Journal article (peer-reviewed)abstract
    • This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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3.
  • Adlarson, Patrik, et al. (author)
  • Abashian-Booth-Crowe resonance structure in the double pionic fusion to He-4
  • 2012
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 86:3, s. 032201-
  • Journal article (peer-reviewed)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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4.
  • Adlarson, Patrik, et al. (author)
  • Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
  • Journal article (peer-reviewed)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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5.
  • Adlarson, Patrik, et al. (author)
  • Backward single-pion production in the pd -> He-3 pi(0)reaction with WASA-at-COSY
  • 2018
  • In: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 54:9
  • Journal article (peer-reviewed)abstract
    • New data on the production of single neutral pions in the pd -> He-3 pi(0) reaction are presented. For fifteen proton beam momenta between p(p) = 1.60GeV/c and p(p) = 1.74 GeV/c, differential cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
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6.
  • Adlarson, Patrik, et al. (author)
  • Differential cross sections for neutron-proton scattering in the region of the d* (2380) dibaryon resonance
  • 2020
  • In: Physical Review C. Nuclear Physics. - : AMER PHYSICAL SOC. - 0556-2813 .- 1089-490X. ; 102:1
  • Journal article (peer-reviewed)abstract
    • Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over barp scattering performed in the energy region of the d* (2380) dibaryon resonance covering the range of beam energies T-n = 0.98-1.29 GeV (root s = 2.32-2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp -> np + p(spectator). In this way the np differential cross section sigma (Theta) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power A(y)(Theta) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled D-3(3) - (3)G(3) waves.
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7.
  • Adlarson, Patrik, et al. (author)
  • Exclusive measurement of the eta -> pi(+) pi(-) gamma decay
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:2, s. 243-249
  • Journal article (peer-reviewed)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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8.
  • Adlarson, Patrik, et al. (author)
  • Importance of d-wave contributions in the charge symmetry breaking reaction dd -> He-4 pi(0)
  • 2018
  • In: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 781, s. 645-650
  • Journal article (peer-reviewed)abstract
    • This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd -> He-4 pi(0) using the WASA-at-COSY detector setup at an excess energy of Q = 60 MeV. The determined differential cross section can be parametrized as d sigma/d Omega = a + b cos(2) theta*, where theta* is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a = (1.55 +/- 0.46(stat)(-0.8)(+0.32)(syst)) pb/sr and b = (13.1 +/- 2.1(stat)(-2.7)(+1.0)(syst)) pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the A isobar to the dd -> He-4 pi(0) reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.
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9.
  • Adlarson, Patrik, et al. (author)
  • Investigation of the dd -> (3)Hen pi(0) reaction with the FZ Julich WASA-at-COSY facility
  • 2013
  • In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:1, s. 014004-
  • Journal article (peer-reviewed)abstract
    • An exclusive measurement of the dd -> (3)Hen pi(0) reaction was carried out at a beam momentum of p(d) = 1.2 GeV/c using the WASA-at-COSY facility. Information on the total cross section as well as differential distributions was obtained. The data are described by a phenomenological approach based on a combination of a quasifree model and a partial wave expansion for the three-body reaction. The total cross section is found to be sigma(tot) = ( 2.89 +/- 0.01(stat) +/- 0.06(sys) +/- 0.29(norm)) mu b. The contribution of the quasifree processes ( with the beam or target neutron being a spectator) accounts for 38% of the total cross section and dominates the differential distributions in specific regions of phase space. The remaining part of the cross section can be described by a partial wave decomposition indicating the significance of p-wave contributions in the final state.
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10.
  • Adlarson, Patrik, et al. (author)
  • Isoscalar single-pion production in the region of Roper and d*(2380) resonances
  • 2017
  • In: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 774, s. 599-607
  • Journal article (peer-reviewed)abstract
    • Exclusive measurements of the quasi-free pn -> pp pi(-) and pp -> pp pi(0) reactions have been performed by means of pd collisions at T-p= 1.2 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region T-p= 0.95-1.3 GeV (root s = 2.3-2.46 GeV), which includes the regions of triangle(1232), N*(1440) and d*(2380) resonance excitations. From these measurements the isoscalar single-pion production has been extracted, for which data existed so far only below T-p = 1 GeV. We observe a substantial increase of this cross section around 1 GeV, which can be related to the Roper resonance N*(1440), the strength of which shows up isolated from the triangle resonance in the isoscalar (N pi)(I=0) invariant-mass spectrum. No evidence for a decay of the dibaryon resonance d*(2380) into the isoscalar (NN pi)(I=0) channel is found. An upper limit of 180 mu b (90% CL.) corresponding to a branching ratio of 9% has been deduced.
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  • Result 1-10 of 32

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