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Sökning: WFRF:(Böse S.)

  • Resultat 1-9 av 9
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1.
  • Alef, S., et al. (författare)
  • Commissioning and initial experimental program of the BGO-OD experiment at ELSA
  • 2016
  • Ingår i: 14th InternationalWorkshop on Meson Production, Properties and Interaction, MESON 2016,Cracow, Poland,2016-06-02 - 2016-06-07. - EDP Sciences.
  • Konferensbidrag (refereegranskat)abstract
    • BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.
2.
  • Alef, S., et al. (författare)
  • The BGOOD experimental setup at ELSA
  • 2020
  • Ingår i: European Physical Journal A. - Springer. - 1434-6001. ; 56:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and strange meson photoproduction, in particular t-channel processes at low momentum transfer. The setup uniquely combines a central almost 4 π acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.
3.
  • Bantes, B., et al. (författare)
  • The BGO calorimeter of BGO-OD experiment
  • 2015
  • Ingår i: Journal of Physics: Conference Series. - IOP Publishing. - 1742-6588. ; 587:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The BGO Rugby Ball is a large solid angle electromagnetic calorimeter now installed in the ELSA Facility in Bonn. The BGO is operating in the BGO-OD experiment aiming to study meson photoproduction off proton and neutron induced by a Bremsstrahlung polarized gamma beam of energies from 0.2 to 3.2 GeV and an intensity of 5 × 107 photons per second. The scintillating material characteristics and the photomultiplier read-out make this detector particularly suited for the detection of medium energy photons and electrons with very good energy resolution. The detector has been equipped with a new electronics read-out system, consisting of 30 sampling ADC Wie-Ne-R modules which perform the off-line reconstruction of the signal start-time allowing for a good timing resolution. Performances in linearity, resolution and time response have been carefully tested at the Beam Test Facility of the INFN National Laboratories in Frascati by using a matrix of 7 BGO crystals coupled to photomultipliers and equipped with the Wie-Ne-R sampling ADCs.
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4.
  • Müller, J., et al. (författare)
  • New data on γ→p→→ηp with polarized photons and protons and their implications for N⁎ → Nη decays
  • 2020
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 803
  • Tidskriftsartikel (refereegranskat)abstract
    • The polarization observables T,E,P,H, and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W=2400 MeV (T), 2280 MeV (E), 1620 MeV (P,H), or 1820 MeV (G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33±0.04 for N(1650)1/2− is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass JP=1/2−-resonances significantly.
5.
  • Nanova, M., et al. (författare)
  • Determination of the real part of the η′ -Nb optical potential
  • 2016
  • Ingår i: Physical Review C. - American Physical Society. - 2469-9985. ; 94:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The excitation function and momentum distribution of η′ mesons have been measured in photoproduction off Nb93 in the energy range of 1.2-2.9 GeV. The experiment has been performed with the combined Crystal Barrel and MiniTAPS detector system, using tagged photon beams from the ELSA electron accelerator. Information on the sign and magnitude of the real part of the η′-Nb potential has been extracted from a comparison of the data with model calculations. An attractive potential of -(41±10(stat)±15(syst)) MeV depth at normal nuclear matter density is deduced within model uncertainties. This value is consistent with the potential depth of -(37±10(stat)±10(syst)) MeV obtained in an earlier measurement for a light nucleus (carbon). This relatively shallow η′-nucleus potential will make the search for η′-nucleus bound states more difficult.
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6.
  • Nanova, M., et al. (författare)
  • The η′-carbon potential at low meson momenta
  • 2018
  • Ingår i: European Physical Journal A. - Springer. - 1434-6001. ; 54:10
  • Tidskriftsartikel (refereegranskat)abstract
    • The production of η′ mesons in coincidence with forward-going protons has been studied in photon-induced reactions on 12 C and on a liquid hydrogen (LH 2 ) target for incoming photon energies of 1.3–2.6 GeV at the electron accelerator ELSA. The η′ mesons have been identified via the η′ → π 0 π 0 η → 6γ decay registered with the CBELSA/TAPS detector system. Coincident protons have been identified in the MiniTAPS BaF 2 array at polar angles of 2°≤ θ p ≤ 11°. Under these kinematic constraints the η′ mesons are produced with relatively low kinetic energy (≈ 150 MeV) since the coincident protons take over most of the momentum of the incident-photon beam. For the C-target this allows the determination of the real part of the η′-carbon potential at low meson momenta by comparing with collision model calculations of the η′ kinetic energy distribution and excitation function. Fitting the latter data for η′ mesons going backwards in the center-of-mass system yields a potential depth of V = −(44 ± 16(stat) ± 15(syst)) MeV, consistent with earlier determinations of the potential depth in inclusive measurements for average η′ momenta of ≈ 1.1 GeV/c. Within the experimental uncertainties, there is no indication of a momentum dependence of the η′-carbon potential. The LH 2 data, taken as a reference to check the data analysis and the model calculations, provide differential and integral cross sections in good agreement with previous results for η′ photoproduction off the free proton.
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7.
  • The CBELSA/TAPS Collaboration, CBELSA/TAPS Collaboration, et al. (författare)
  • Momentum dependence of the imaginary part of the ω - and η -nucleus optical potential
  • 2016
  • Ingår i: European Physical Journal A. - Springer. - 1434-6001. ; 52:9
  • Tidskriftsartikel (refereegranskat)abstract
    • The photoproduction of ω and η mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9GeV at the electron accelerator ELSA. The mesons have been identified via the ω → π0 γ → 3 γ and η → π0η → 6 γ decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium ω and η widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium ω width and η-N absorption cross sections. The energy dependence of the imaginary part of the ω- and η-nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the η-nucleus potential is found to be about three times smaller than recently determined values of the real part of the η-nucleus potential, which makes the η meson a suitable candidate for the search for meson-nucleus bound states. For the ω meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected, which makes the observation of ω mesic states very difficult experimentally.
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8.
  • Hartmann, J., et al. (författare)
  • N (1520) 3 /2- helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions
  • 2014
  • Ingår i: Physical Review Letters. - American Physical Society. - 0031-9007. ; 113:6
  • Tidskriftsartikel (refereegranskat)abstract
    • New data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.
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9.
  • Hartmanna, J., et al. (författare)
  • The polarization observables T, P, and H and their impact on γp → pπ0 multipoles
  • 2015
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 748, s. 212-220
  • Tidskriftsartikel (refereegranskat)abstract
    • Data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.
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