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Träfflista för sökning "WFRF:(Annand J. R. M.) "

Sökning: WFRF:(Annand J. R. M.)

  • Resultat 1-10 av 42
  • [1]2345Nästa
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1.
  • Alcorn, J, et al. (författare)
  • Basic instrumentation for Hall A at Jefferson Lab
  • 2004
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier. - 0167-5087. ; 522:3, s. 294-346
  • Tidskriftsartikel (refereegranskat)abstract
    • The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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2.
  • Chirapatpimol, K, et al. (författare)
  • Precision Measurement of the p(e,e′p)π0 Reaction at Threshold
  • 2015
  • Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114. ; 114:19
  • Tidskriftsartikel (refereegranskat)abstract
    • New results are reported from a measurement of π^{0} electroproduction near threshold using the p(e,e^{'}p)π^{0} reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the ϕ_{π}^{*} and θ_{π}^{*} angles in the pπ^{0} center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. The 4-momentum transfer Q^{2} coverage ranges from 0.05 to 0.155 (GeV/c)^{2} in fine steps. A simple phenomenological analysis of our data shows strong disagreement with p-wave predictions from ChPT for Q^{2}>0.07 (GeV/c)^{2}, while the s-wave predictions are in reasonable agreement.
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3.
  • Aguar-Bartolome, P., et al. (författare)
  • Measurement of the gamma p -> K-0 Sigma(+) reaction with the Crystal Ball/TAPS detectors at the Mainz Microtron
  • 2013
  • Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813. ; 88:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The gamma p -> K-0 Sigma(+) reaction has been measured from threshold to E-gamma = 1.45 GeV (W-CM = 1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3 pi(0)p final state, by assuming K-S(0) -> pi(0)pi(0) and Sigma(+) -> pi(0)p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the gamma p -> K-0 Sigma(+) reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present gamma p -> K-0 Sigma(+) results to existing data allowed a better description of this reaction with various models.
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4.
  • Aguar-Bartolome, P., et al. (författare)
  • New determination of the eta transition form factor in the Dalitz decay eta -> e(+) e(-) gamma with the Crystal Ball/TAPS detectors at the Mainz Microtron
  • 2014
  • Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813. ; 89:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The Dalitz decay eta -> e(+) e(-) gamma has been measured in the gamma p -> eta p reaction with the Crystal Ball and TAPS multiphoton spectrometers, together with the photon-tagging facility at the Mainz Microtron MAMI. The experimental statistic used in this work is one order of magnitude greater than in any previous measurement of eta -> e(+) e(-) gamma. The value obtained for the slope parameter Lambda(-2) of the eta transition form factor, Lambda(-2) = (1.95 +/- 0.15(stat) +/- 0.10(syst)) GeV-2, is in good agreement with recent measurements conducted in eta -> e(+) e(-) gamma and eta -> mu(+) mu(-) gamma decays, as well as with recent form-factor calculations. The uncertainty obtained in the value of Lambda(-2) is lower compared to results from previous measurements of the eta -> e(+) e(-) gamma decay.
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5.
  • Kashevarov, V. L., et al. (författare)
  • Experimental study of the gamma p -> pi (0)pi(0) p reaction with the Crystal Ball/TAPS detector system at the Mainz Microtron
  • 2012
  • Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813. ; 85:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The gamma p -> pi(0)pi(0) p reaction has been measured from threshold to 1.4 GeV using the Crystal Ball and TAPS photon spectrometers together with the photon tagging facility at the Mainz Microtron. The experimental results include total and differential cross sections as well as specific angular distributions, which were used to extract partial-wave amplitudes. In particular, the energy region below the D-13(1520) resonance was studied.
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6.
  • Myers, L. S., et al. (författare)
  • Compton scattering from C-12 using tagged photons in the energy range 65-115 MeV
  • 2014
  • Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813. ; 89:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Elastic scattering of photons from C-12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60 degrees, 120 degrees, and 150 degrees. at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the C-12(gamma,gamma)C-12 cross section to the bound- nucleon polarizabilities.
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7.
  • Rofors, E., et al. (författare)
  • Response of a Li-glass/multi-anode photomultiplier detector to focused proton and deuteron beams
  • 2020
  • Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier. - 0168-9002. ; 984
  • Tidskriftsartikel (refereegranskat)abstract
    • The response of a position-sensitive Li-glass based scintillation detector being developed for thermal-neutron detection with 6 mm position resolution has been investigated using focused beams of 2.5MeV protons and deuterons. The beams were scanned across the detector in 0.5 mm horizontal and vertical steps perpendicular to the beams. Scintillation light was registered using an 8 × 8 pixel multi-anode photomultiplier tube. The signal amplitudes were recorded for each pixel on an event-by-event basis. Several pixels generally registered considerable signals at each beam location. To optimize planned detector operation at the European Spallation Source, the number of pixels above set thresholds was investigated, with the maximization of the single-hit efficiency over the largest possible area as the primary goal. For both beams, at a threshold of ∼50% of the mean of the full-deposition peak, ∼80% of the events were registered in a single pixel, resulting in an effective position resolution of ∼5 mm in X and Y. Lower thresholds resulted in higher pixel multiplicities. These events could also be localized with the same effective position resolution.
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8.
  • Dutz, H, et al. (författare)
  • Experimental check of the Gerasimov-Drell-Hearn sum rule for H-1
  • 2004
  • Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114. ; 93:3
  • Tidskriftsartikel (refereegranskat)abstract
    • For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] mub with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.
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9.
  • Dutz, H, et al. (författare)
  • First measurement of the Gerasimov-Drell-Hearn sum rule for H-1 from 0.7 to 1.8 GeV at ELSA
  • 2003
  • Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114. ; 91:19: 192001
  • Tidskriftsartikel (refereegranskat)abstract
    • To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] mub.
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10.
  • Dutz, H, et al. (författare)
  • Measurement of helicity-dependent photoabsorption cross sections on the neutron from 815 to 1825 MeV
  • 2005
  • Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114. ; 94
  • Tidskriftsartikel (refereegranskat)abstract
    • Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4 pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat)+/- 4.5(syst)] mu b is extracted.
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  • Resultat 1-10 av 42
  • [1]2345Nästa

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